Hi i just read about the i9295 and the i537 and they are the same device accept the different in the frameware version (the i9295 - 4.2.2, i537 - 4.4.2).
so i have the question can i install the i537 4.4.2 stock rom on the i9295?
and if not i'll be happy if you can explain why (just so i can understand).
thanx ahead! :laugh:
solokiller11 said:
Hi i just read about the i9295 and the i537 and they are the same device accept the different in the frameware version (the i9295 - 4.2.2, i537 - 4.4.2).
so i have the question can i install the i537 4.4.2 stock rom on the i9295?
and if not i'll be happy if you can explain why (just so i can understand).
thanx ahead! :laugh:
Click to expand...
Click to collapse
While the i9295 and the i537 have the same hardware, they have different software. More specifically, the i9295 has an unlocked bootloader while the i537 has a locked bootloader. What this means is that the i9295 is able to flash/install a custom recovery, custom kernel, and custom ROM while on the i537, in order to flash anything it must be signed by Samsung. Only official firmware is signed by Samsung, so there is no way to flash a custom recovery or custom kernel. There is a way to flash custom ROMs, but that's not important here.
To answer you question, theoretically you could flash the i537 firmware on your i9295, but you will most likely end up with a bricked phone because bootloaders are only compatible with their intended models. So the i537 bootloader will only work with the i537 and will brick the i9295.
If you still really want the i537 4.4.2 firmware on your phone, I'd be more than happy to trade my i537 for your i9295. This is a great phone and works great in every respect, I only wish it had an unlocked bootloader like the i9295. If I could do it all over again I would have bought the i9295 instead.
EDIT: I think @mythi is working on a stock 4.4 ROM for the i9295, you might want to ask him about it.
Devo7v said:
While the i9295 and the i537 have the same hardware, they have different software. More specifically, the i9295 has an unlocked bootloader while the i537 has a locked bootloader. What this means is that the i9295 is able to flash/install a custom recovery, custom kernel, and custom ROM while on the i537, in order to flash anything it must be signed by Samsung. Only official firmware is signed by Samsung, so there is no way to flash a custom recovery or custom kernel. There is a way to flash custom ROMs, but that's not important here.
To answer you question, theoretically you should be able to flash the i537 firmware on your i9295, but you will end up with a locked bootloader and no way to revert it. Your phone would still work and you'd still be able to use it, but it would be locked down so that you'd only be able to use AT&T firmware. If you really want 4.4 on your phone, I suggest you flash one of the custom ROMs in the development section.
If you still really want the 4.4.2 firmware on your phone, I'd be more than happy to trade my i537 for your i9295. This is a great phone and works great in every respect, I only wish it had an unlocked bootloader like the i9295. If I could do it all over again I would have bought the i9295 instead.
EDIT: I think @mythi is working on a stock 4.4 ROM for the i9295, you might want to ask him about it.
Click to expand...
Click to collapse
Hi thank you very much for your answer it helped me a lot.
and about the locked bootloader, are you sure that it can't be revert?
and one more thing i bought this phone like two weeks ago so what is the best custom rom for now? (i saw only the carbon rom 4.4.2)
and one more question, if the i537 4.4.2 is signed by samsung but with locked bootloader and the i9295 4.2.2 is also signed by samsung and with unlocked bootloader so cant i just flash back the i9295 framewere over the i537 framewere?
solokiller11 said:
Hi thank you very much for your answer it helped me a lot.
and about the locked bootloader, are you sure that it can't be revert?
and one more thing i bought this phone like two weeks ago so what is the best custom rom for now? (i saw only the carbon rom 4.4.2)
Click to expand...
Click to collapse
Once you have a locked bootloader, the only way to get another bootloader on the phone is to flash one that has been signed by Samsung. Samsung uses a different signature on unlocked bootloaders, so there is no way to revert.
I don't think you really looked? I just opened the Development forum and found the following on the first page:
[S4-I9295● KK 4.4.2][05.05 M1][SOKP》》SONIC OPEN KANG PROJECT][AIO][Weekly Builds]
[Rom] Updated [Unofficial] Carbon Rom 4.4.2 based on CM11.0 [24.04.14]
[Rom] [Unofficial] BeanStalk 4.4.2 based on CM11.0 [24.04.14]
[ROM][4.4.2]Unofficial Dirty AOSB Build]
[ROM] 4.4.2 | MoKee Opensource | CM & AOSP | HALO][Dirty-Build]
[ROM][4.4.2][Unofficial Dirty SlimBean Build][New Build Available][Slim Weekly 3.0]
In the Original Development forum there is [ROM][Unofficial/Experimental][Android 4.4] CyanogenMod 11.0 for SGS4A (int'l). It's under constant development and I hear good things about it, but again, I have an i537 so I can't try any of these.
Devo7v said:
Once you have a locked bootloader, the only way to get another bootloader on the phone is to flash one that has been signed by Samsung. Samsung does not sign unlocked bootloaders, so there is no way to revert.
I don't think you really looked? I just opened the Development forum and found the following on the first page:
[S4-I9295● KK 4.4.2][05.05 M1][SOKP》》SONIC OPEN KANG PROJECT][AIO][Weekly Builds]
[Rom] Updated [Unofficial] Carbon Rom 4.4.2 based on CM11.0 [24.04.14]
[Rom] [Unofficial] BeanStalk 4.4.2 based on CM11.0 [24.04.14]
[ROM][4.4.2]Unofficial Dirty AOSB Build]
[ROM] 4.4.2 | MoKee Opensource | CM & AOSP | HALO][Dirty-Build]
[ROM][4.4.2][Unofficial Dirty SlimBean Build][New Build Available][Slim Weekly 3.0]
In the Original Development forum there is [ROM][Unofficial/Experimental][Android 4.4] CyanogenMod 11.0 for SGS4A (int'l). It's under constant development and I hear good things about it, but again, I have an i537 so I can't try any of these.
Click to expand...
Click to collapse
If Samsung doesnt sign unlocked bootloaders so how the i9295 have one?
and thank you for the custom roms
solokiller11 said:
If Samsung doesnt sign unlocked bootloaders so how the i9295 have one?
and thenk you for the custom roms
Click to expand...
Click to collapse
The just flash it to the phone. To simplify the way the bootloader works, it is the first thing that loads when you power on the phone, it then tells the phone what other pieces of software to load (aboot, sbl, kernel, etc.).
With an unlocked bootloader, it does just that, it loads the next piece of software during the booting of the phone. With a locked bootloader, the bootloader checks the signature of the next piece of software to load, if the signature matches the signature that the bootloader expects then the next piece of software loads. If the signature doesn't match, then booting stops.
When you flash something to the phone using Odin (currently the way you flash bootloaders), with an unlocked bootloader Odin will flash it, for better or worse. But with a locked bootloader, the bootloader checks the signature of the file you are trying to flash and if they match then it can be flashed, if it doesn't match then the flash aborts without any changes being made.
So, how can Samsung put an unlocked bootloader on the phone without it being signed? When you start with empty hardware you can essentially put any software you want on the phone, there is nothing there preventing it, but once you put a locked bootloader on the phone if will then check every single piece of software you try to flash to the phone.
TL;DR Think of the hardware as an empty room. You can put anything you want in the room to start with, but if the first thing you put in the room is a door with a lock, then the only things you can put in the room from then on are things that have a key to that lock.
Devo7v said:
The just flash it to the phone. To simplify the way the bootloader works, it is the first thing that loads when you power on the phone, it then tells the phone what other pieces of software to load (aboot, sbl, kernel, etc.).
With an unlocked bootloader, it does just that, it loads the next piece of software during the booting of the phone. With a locked bootloader, the bootloader checks the signature of the next piece of software to load, if the signature matches the signature that the bootloader expects then the next piece of software loads. If the signature doesn't match, then booting stops.
When you flash something to the phone using Odin (currently the way you flash bootloaders), with an unlocked bootloader Odin will flash it. But with a locked bootloader, the bootloader checks the signature of the file you are trying to flash and if they match then it can be flashed, if it doesn't match then the flash aborts without any changes being made.
So, how can Samsung put an unlocked bootloader on the phone without it being signed? When you start with empty hardware you can essentially put any software you want on the phone, there is nothing there preventing it, but once you put a locked bootloader on the phone if will then check every single piece of software you try to flash to the phone.
TL;DR Think of the hardware as an empty room. You can put anything you want in the room to start with, but if the first thing you put in the room is a door with a lock, then the only things you can put in the room from then on are things that have a key to that lock.
Click to expand...
Click to collapse
Hi man Thank you very very much for the explanation about the bootloaders and i think i gonna install the carbon rom
Devo7v said:
While the i9295 and the i537 have the same hardware, they have different software. More specifically, the i9295 has an unlocked bootloader while the i537 has a locked bootloader. What this means is that the i9295 is able to flash/install a custom recovery, custom kernel, and custom ROM while on the i537, in order to flash anything it must be signed by Samsung. Only official firmware is signed by Samsung, so there is no way to flash a custom recovery or custom kernel. There is a way to flash custom ROMs, but that's not important here.
To answer you question, theoretically you should be able to flash the i537 firmware on your i9295, but you will end up with a locked bootloader and no way to revert it. Your phone would still work and you'd still be able to use it, but it would be locked down so that you'd only be able to use AT&T firmware. If you really want 4.4 on your phone, I suggest you flash one of the custom ROMs in the development section.
If you still really want the 4.4.2 firmware on your phone, I'd be more than happy to trade my i537 for your i9295. This is a great phone and works great in every respect, I only wish it had an unlocked bootloader like the i9295. If I could do it all over again I would have bought the i9295 instead.
EDIT: I think @mythi is working on a stock 4.4 ROM for the i9295, you might want to ask him about it.
Click to expand...
Click to collapse
NONONONONONONO ... never ever i say never ever repeat what u said in here ... flashing a other devices bootloader will destroy your phone and you will need something called jig to fix it ... this happens because every device that sammy realeses has a private key for certain partitions on the mmc like the bootloader the rbm etc ... flashing other devices partitions even if the share the same hardware (yes) even if they are from the same family will kill your phone and you will end with a paper that need 200$ service . i request you to edit your comment since alot of the people here are noobs or have little knowelge .
mythi said:
NONONONONONONO ... never ever i say never ever repeat what u said in here ... flashing a other devices bootloader will destroy your phone and you will need something called jig to fix it ... this happens because every device that sammy realeses has a private key for certain partitions on the mmc like the bootloader the rbm etc ... flashing other devices partitions even if the share the same hardware (yes) even if they are from the same family will kill your phone and you will end with a paper that need 200$ service . i request you to edit your comment since alot of the people here are noobs or have little knowelge .
Click to expand...
Click to collapse
I'm going to edit my post, but I'm also going to disagree with you. Back when I had a Samsung Captivate you were able to flash Galaxy S i9000 ROMs with some minor tweaks. Inadvertently I accidentally flashed an i9000 one-click to my i897. The flash finished and my was messed up, but not so bad that it made the phone unusable (i.e. buttons were mapped incorrectly and the display was inverted). I discovered I had installed an i9000 bootloader on my phone because the partitions were different and I couldn't boot the phone after flashing i897 stock firmware. The only way I could get stock firmware back on my phone was to flash i897 bootloaders which lead me to believe that my phone had the i9000 bootloader on it. Maybe I'm wrong and maybe Samsung has changed the way things work in the past 4 years, but I do not believe this was always the case.
That said, I will make sure that everybody understands that they could brick their phone if they flash a different bootloader.
Devo7v said:
I'm going to edit my post, but I'm also going to disagree with you. Back when I had a Samsung Captivate you were able to flash Galaxy S i9000 ROMs with some minor tweaks. Inadvertently I accidentally flashed an i9000 one-click to my i897. The flash finished and my was messed up, but not so bad that it made the phone unusable (i.e. buttons were mapped incorrectly and the display was inverted). I discovered I had installed an i9000 bootloader on my phone because the partitions were different and I couldn't boot the phone after flashing i897 stock firmware. The only way I could get stock firmware back on my phone was to flash i897 bootloaders which lead me to believe that my phone had the i9000 bootloader on it. Maybe I'm wrong and maybe Samsung has changed the way things work in the past 4 years, but I do not believe this was always the case.
That said, I will make sure that everybody understands that they could brick their phone if they flash a different bootloader.
Click to expand...
Click to collapse
Well the captivate is another story the developers got a leak of a signed rbm of the chipset of (i suspect) the humming bird chipset ... when you have something like that minor modifications can be done ... the same happened a while ago with some 8xx and i not sure of the 6xx -which runs in our phones- the leaked rbm would help devs to make other variants easily compatible in the low level side .
bootloaders :good:are also different story ... each and every device these days has a private key as i said earlier this key gets checked before booting by something in chipset (hardware side) and if key mismatch the device will enter a qcom mode for debugging etcetcetcetc........
trust me you don't want to brick a 600$ for simply to flash a bootloader :good:
mythi said:
Well the captivate is another story the developers got a leak of a signed rbm of the chipset of (i suspect) the humming bird chipset ... when you have something like that minor modifications can be done ... the same happened a while ago with some 8xx and i not sure of the 6xx -which runs in our phones- the leaked rbm would help devs to make other variants easily compatible in the low level side .
bootloaders :good:are also different story ... each and every device these days has a private key as i said earlier this key gets checked before booting by something in chipset (hardware side) and if key mismatch the device will enter a qcom mode for debugging etcetcetcetc........
trust me you don't want to brick a 600$ for simply to flash a bootloader :good:
Click to expand...
Click to collapse
Thanks for the info. So here a related question, what would happen if you took an i9295 with 4.2.2 on it and flashed the i537 4.2.2 firmware minus the bootloader? Would it fail to boot due to partitioning or would it work?
mythi said:
NONONONONONONO ... never ever i say never ever repeat what u said in here ... flashing a other devices bootloader will destroy your phone and you will need something called jig to fix it ... this happens because every device that sammy realeses has a private key for certain partitions on the mmc like the bootloader the rbm etc ... flashing other devices partitions even if the share the same hardware (yes) even if they are from the same family will kill your phone and you will end with a paper that need 200$ service . i request you to edit your comment since alot of the people here are noobs or have little knowelge .
Click to expand...
Click to collapse
hi man i dont think you right because my last phone was xtreamer joyz which is the exact same phone as the newman n2 and i could install both official framewere with no problem and those two phones have the exact same specs and also the i537 and the i9295 so i think it should work just fine.
but my knowelge isnt good as yours so correct me if im wrong here but i think it should work
EDIT: I still asking my question but also joining to Devo7v question about what will happen.
Devo7v said:
Thanks for the info. So here a related question, what would happen if you took an i9295 with 4.2.2 on it and flashed the i537 4.2.2 firmware minus the bootloader? Would it fail to boot due to partitioning or would it work?
Click to expand...
Click to collapse
If we get a way of unlocking the bootloader we can do this ... I will explain further ...
A stock Sammy ROM comes in the form of a tar.md5 package the .md5 part holds the signature of Sammy , this signature is a type of code that makes the bootloader understand that this package is a signed one with a Sammy key ... When we take the bootloader out of The package (sbl1.bin , sbl2.bin and sbl3.bin) we have to take other parts such as the rbm after taking these we have to repackage the remaining parts in a new tar package ... After doing this we can sign it with an md5 key but this key will give missmatch errors during flash so we have to get the keys of Sammy ... Even if we find those we will have find away to unlock the bootloader to unlock more things
mythi said:
If we get a way of unlocking the bootloader we can do this ... I will explain further ...
A stock Sammy ROM comes in the form of a tar.md5 package the .md5 part holds the signature of Sammy , this signature is a type of code that makes the bootloader understand that this package is a signed one with a Sammy key ... When we take the bootloader out of The package (sbl1.bin , sbl2.bin and sbl3.bin) we have to take other parts such as the rbm after taking these we have to repackage the remaining parts in a new tar package ... After doing this we can sign it with an md5 key but this key will give missmatch errors during flash so we have to get the keys of Sammy ... Even if we find those we will have find away to unlock the bootloader to unlock more things
Click to expand...
Click to collapse
I have to say that i didn't really understand why i cant install the official samsung i537 over the official samsung i9295 because the both signed by Samsung.
like if i have flashed the i9295 4.2.2 official stock on my i9295 so i can flash the i537 4.4.2 official stock no? they both have the Samsung key no?
solokiller11 said:
I have to say that i didn't really understand why i cant install the official samsung i537 over the official samsung i9295 because the both signed by Samsung.
like if i have flashed the i9295 4.2.2 official stock on my i9295 so i can flash the i537 4.4.2 official stock no? they both have the Samsung key no?
Click to expand...
Click to collapse
So u have a gt-i9295 i thought you have i537 :crying::crying: any way that can be possible as i did it already just wait and you will get it ... i have ensured it won't brick any phone but wifi and camera are not working
mythi said:
So u have a gt-i9295 i thought you have i537 :crying::crying: any way that can be possible as i did it already just wait and you will get it ... i have ensured it won't brick any phone but wifi and camera are not working
Click to expand...
Click to collapse
Hi thank you very much for your answer :laugh:.
And if I will choose to install the i537 4.4.2 on my i9295 do you know if i can fix the camera and the wifi?
solokiller11 said:
Hi thank you very much for your answer :laugh:.
And if I will choose to install the i537 4.4.2 on my i9295 do you know if i can fix the camera and the wifi?
Click to expand...
Click to collapse
I don't have any idea what must be done ... But I need to investigate more on this .
Hello, I currently have a few Samsungs (old, S3), and they are all rooted (I am familiar with rooting, firmware loading via Odin, TWRP/CWM, etc). I have read a large number of posts on how the Galaxy S5 after 5.X is boot loader locked. I was gifted with a AT&T Samsung Galaxy S5, with the Sim unlock code (and I would like to use it), however, it has been updated to G900AUCS4CPA2. To add insult to injury, I am on T-Mobile.
Forum posts have indicated that the only requirement to move to T-Mobile is to change the sim. However, it would be nice to use the wifi calling, etc (or at least a T-Mobile rom). Even though the bootloader is locked, is there a way to install a Tmobile S5 5.X or 6.X rom? It seems like installing different AT&T roms via Odin is possible, as long as they are >=5.X. Is there a way to install a T-Mobile rom via Odin?
Barring all of that, is there a way to install a totally generic rom, and not be AT&T branded/bloated/etc?
Thank you.
No. The locked bootloader prevents all of that.
shortydoggg said:
No. The locked bootloader prevents all of that.
Click to expand...
Click to collapse
Ok, but it came with 6.0 and I downgraded to PA2. So there is no way to install anything else?
Backstory: I initially tried and failed to install 4.4.2, and with more reading realized that I was on the "bootloader locked" 6.0, and that I had thrashed the current rom that was installed. I then found an XDA post on moving back to 6.0, but it starts with PA2, which installed successfully and the phone is on PA2 (the rom I posted in the beginning of the thread). So, I can seemingly install AT&T roms, as long as they are 5.0+?? I just can not move anywhere else??
Thank you for your input.
This is one of two phones I'm looking to buy after work today to replace the Verizon S5 I broke last night. Wanting to make sure whatever I get can be bootloader unlocked and fully rooted, otherwise I'm just getting another S5 so I can continue using CM ROM.
Thanks!
i think yes following this steps
1-root it using pinpong root
2-unlock the boot loader using ADB on pc
3-install twrp
4-install SU
watch the video it did it with a note 4
https://www.youtube.com/watch?v=OoxWDDEFJxQ
johnnyrichter said:
This is one of two phones I'm looking to buy after work today to replace the Verizon S5 I broke last night. Wanting to make sure whatever I get can be bootloader unlocked and fully rooted, otherwise I'm just getting another S5 so I can continue using CM ROM.
Thanks!
Click to expand...
Click to collapse
No.
No bootloader unlock at all.
Therefore no non stock based custom roms.
Root is available via ping-pong on very early lollipop builds, but unless you specifically know you are getting an old, non updated device, it's not likely this will be an option. Some newer builds of lollipop can be rooted by a tethered method. There is a root method for some MM builds. Think one is under development that has yet to be confirmed or released for N.
Very strongly do not recommend ATT version of this device if rooting and custom ROM's are important to you.
If you're looking at an international, rather than att model, then you're in the wrong forum.
Hi, im new to Note 5 Dev. and been out of the loop since it was released. i had a Sony Xperia play and a Galaxy s3 before and know how to do the basic stuff to do custom roms and flash stuff etc. to those Phones. But a Note 5 is different, running on Lollipop, having EFS partition stuff and OEM unlock Stuff. i just want to ask a few questions to make sure i don't do something stupid (i already did some of the research for answers on some of this for a few days now and some are Informative and Awesome, but a little outdated) so tnx in advance kind People :fingers-crossed:
My Device: SM-N920C (UAE)
Android Ver: 5.1.1 (Lollipop) Stock
Questions:
1.) Can i Revert back to 5.1.1 (lollipop) stock/ [Downgrade] , IF i decided to update to Nougat Stock?? (just curious ) and if yes, can you kindly link me to a process? if not, then that's fine too :laugh:
2.) Do you have to Enable OEM unlock if Updating Stock (in my case Nougat)??
I red somewhere on Magisk thread here on XDA that it can Grant Root Access to 5.0+ . If so, installing TWRP and Flashing Magisk on 5.1.1 involves Enabling USB Debugging and OEM Unlock.
3.) Do i have to Enable OEM Unlock Forever now? cause i saw some threads says that if you disable it, you will have a bootloop or a soft brick and will have to Flash Stock again and repeat. (don't really have a problem with it being Enabled, but the other people in Tutorials , Vid. Tutorials and Thread Posts just mentions "Enable it". And never really says after the process is done u can Disable it and stuff.), just want to have that information, cause i Understand that OEM is a LOCK that Even if someone steals your phone and has a lock in it. they can't just Flash a Stock Rom on it to Unlock it. [great feature] :fingers-crossed:
4.) if i have a Custom Recovery and Rooted my phone ver. 5.1.1 successfully, can i still Unroot it and go back to Stock 5.1.1?? also applies to other Versions of android. EX. nougat Stock then i root it, will i still unroot it and go back to stock?
5.) Do you need to be in a Specific Version of android to use the Custom Roms?? i mean i'm in android 5.1.1 [if rooted], can i flash a Nougat Custom Rom or a s8 port etc.?? or do i need to be in Stock Nougat > Root it > then flash Custom Nougat Roms?
That is all, Sorry if all the Questions are Freakin Long Shahaha, i just want to be specific so all the people who are also newbies can understand the questions and have answers. Tnx again for the people who have the patience to read and answer these questions. :highfive:
shadowhog006 said:
Hi, im new to Note 5 Dev. and been out of the loop since it was released. i had a Sony Xperia play and a Galaxy s3 before and know how to do the basic stuff to do custom roms and flash stuff etc. to those Phones. But a Note 5 is different, running on Lollipop, having EFS partition stuff and OEM unlock Stuff. i just want to ask a few questions to make sure i don't do something stupid (i already did some of the research for answers on some of this for a few days now and some are Informative and Awesome, but a little outdated) so tnx in advance kind People :fingers-crossed:
My Device: SM-N920C (UAE)
Android Ver: 5.1.1 (Lollipop) Stock
Questions:
1.) Can i Revert back to 5.1.1 (lollipop) stock/ [Downgrade] , IF i decided to update to Nougat Stock?? (just curious ) and if yes, can you kindly link me to a process? if not, then that's fine too :laugh:
2.) Do you have to Enable OEM unlock if Updating Stock (in my case Nougat)??
I red somewhere on Magisk thread here on XDA that it can Grant Root Access to 5.0+ . If so, installing TWRP and Flashing Magisk on 5.1.1 involves Enabling USB Debugging and OEM Unlock.
3.) Do i have to Enable OEM Unlock Forever now? cause i saw some threads says that if you disable it, you will have a bootloop or a soft brick and will have to Flash Stock again and repeat. (don't really have a problem with it being Enabled, but the other people in Tutorials , Vid. Tutorials and Thread Posts just mentions "Enable it". And never really says after the process is done u can Disable it and stuff.), just want to have that information, cause i Understand that OEM is a LOCK that Even if someone steals your phone and has a lock in it. they can't just Flash a Stock Rom on it to Unlock it. [great feature] :fingers-crossed:
4.) if i have a Custom Recovery and Rooted my phone ver. 5.1.1 successfully, can i still Unroot it and go back to Stock 5.1.1?? also applies to other Versions of android. EX. nougat Stock then i root it, will i still unroot it and go back to stock?
5.) Do you need to be in a Specific Version of android to use the Custom Roms?? i mean i'm in android 5.1.1 [if rooted], can i flash a Nougat Custom Rom or a s8 port etc.?? or do i need to be in Stock Nougat > Root it > then flash Custom Nougat Roms?
That is all, Sorry if all the Questions are Freakin Long Shahaha, i just want to be specific so all the people who are also newbies can understand the questions and have answers. Tnx again for the people who have the patience to read and answer these questions. :highfive:
Click to expand...
Click to collapse
1)If you flash stock 7.0 on your device if available then its hard to revert to back to stock 5.1.1 as there is thread in Question&Answers section about downgrading from 6.0.1 to 5.1.1 but many are unsuccessful(I have successfully downgraded from 7.0 to 6.0.1 but Cant confirm about 5.1.1 as google has changed many security policies in updates versions like 6.0.1 or 7.0 which will block your bootloader to downgrade easily/Issue you will face like lossing of baseband or corrupt imei which will block you from receiving network signal)
2)Yes its very important to enable Oem unlock and usb debugging while flashing any stock firmware using odin to avoid DM-Verity/SW Check Fail/Custom Binary blocked by FRP like issues which are hard to solve enough OR you will might hard brick your device which will be difficult to make it live again( AFAIK to flash TWRP or Any root access using odin there is instruction to enable Oem Unlock before flashing always remember it as a essential step before flashing anything using odin)
3)Yes once you enable Oem unlock for purpose of modification of your device, it needs to be unlocked or even its enabled by default to overcome reported issue like infinite bootloop or Many i mentioned in my 2nd Post And Oem unlock allows your bootloader to be customised by flashing mods or roms which is by default locked so that you could not easily modify your device as well as to avoid further modification issues
4)If you choose to stay at 5.1.1 and rooted your device with installed TWRP then yes you can unroot it by flashing 5.1.1 using odin( In case your on 6.0.1 or Even on 7.0 you can unroot your device with the same process but here to remind you that you need to flash stock 6.0.1 or 7.0 respectively version on which you rooted your device So if you will try to unroot it by flashing 5.1.1 again while your on 7.0 rooted device then again here downgrade issue which will probably give you mentioned error as a result)
5)To use custom nougat based roms or any S8+ port based on 7.0 you should atleast upgrade your bootloader and modem to 6.0.1( If your rooted on 5.1.1 and try installing nougat roms then your device will not boot as your using old bootloader, so upgrade bootloader or modem either to 6.0.1 or you can update whole system to 7.0>root>install TWRP>flash custom nougat based roms or s8+ ports afterall choice is your as if you want to upgrade only BL and Modem to 6.0.1 or want to upgrade system with BL and Modem to 7.0, i will mention here is BL and Modem for 7.0 are also available to flash you can find those on dr.ketan rom n10 installation instruction section in Samsung galaxy note 5>Android development>Dr.ketan Rom N10 instead of whole system update but Flashing Stock full firmware is always recommended for good reception and avoid glitches)
I think i have tried to fulfil all of your queries as far possible by myself
Regards,
AssassinCreed-Xda Developers
Too bad about the answer to the 3rd question, that feature would've been nice to have. but oh well. shahahaha
~Ooh!! i have a follow up question regarding your Answer to the 4th question. Can i also flash other Countries Stock firmware?? for example: mine is Stock 5.1.1 [UAE] can i flash Stock 5.1.1 [USA] or other Country variants?? [of course unlocked bootloader] , i searched again here for people who did that and for some reason they encounter Errors and Unable to revert back to their Original Stock Firmwares.
@AssassinCreed Thank you. yup, clear cut answers. Thank you!! :victory: :victory: