[Q] [CM12.1] Downgrade from CM13.1 - HELP -

[Jaccob25]

Hi everyone. I was read a lot off discussions about i9100 with CM12.1 but I still don't know how to do it without some problems.
My phone actually running CM13.1 latest nightly build with Team Win TWRP recovery v 2.8.XXX and maybe DorimanX kernel? I don't know how to find Kernel name and version... I would like to ask you how to go to Cm12.1 build with pico or nano GAPPS (And what build I should download). I need the most stable build for daily use. Next how to replace CM recovery with TWRP 3.0.2. . I am totally confused. I'll be glad for any help.

 

[maksymmakarec]

Oh. I have that problem too. CM 13.1 not stable!

 

[noppy22]

Hi everyone. I was read a lot off discussions about i9100 with CM12.1 but I still don't know how to do it without some problems.
My phone actually running CM13.1 latest nightly build with Team Win TWRP recovery v 2.8.XXX and maybe DorimanX kernel? I don't know how to find Kernel name and version... I would like to ask you how to go to Cm12.1 build with pico or nano GAPPS (And what build I should download). I need the most stable build for daily use. Next how to replace CM recovery with TWRP 3.0.2. . I am totally confused. I'll be glad for any help.

Firstly look under settings -> about device and it will tell you the kernel version. If it says 3.0.101-CM------, you have the stock CM13 kernel. You said you have TWRP 2.8.x.x and not CM recovery?? This means you already have the isorec recovery enabled. All you need to do is flash the 3.0.2-1 .img from this recovery and you will have the newer one installed. And just do normal backup/wipes and install CM12.1 as you would any other rom. Just remember to use 5.1 gapps(arm;5.1;pico/nano)

Here is the last official CM12.1 I uploaded

Here is a more up to date unofficial CM12.1

 

[Jaccob25]

Firstly look under settings -> about device and it will tell you the kernel version...

Yes I have stock cm13 kernel and TWRP flashed. Can I flash new TWRP via Odin?
Thank you very much!

 

[noppy22]

Yes I have stock cm13 kernel and TWRP flashed. Can I flash new TWRP via Odin?
Thank you very much!

I don't think you can flash a .img file with odin. Honestly if you want to downgrade to 5.1.1 it would be easier to do it in one go.
Flash CM12.1, gapps, then TWRP 3.0.2-1.img all from TWRP 2.8

 

[Jaccob25]

I don't think you can flash a .img file with odin. Honestly if you want to downgrade to 5.1.1 it would be easier to do it in one go.
Flash CM12.1, gapps, then TWRP 3.0.2-1.img all from TWRP 2.8

Ohh I thought that TWRP can't flash img file.
Thanks for advice. I try it today.

 

[Jaccob25]

So I try that and almost everything works fine. Only GPS fixing seems like a little bit problematic. But I don't know my testing was short. I will see.

 

[teraghik]

May I ask a supplementary question - I am in a similar position, I have an i9100 which I upgraded from stock 4.1.2 Jelly Bean to CM13 following (most of) djibe's guide here
So I now have CM13 ROM with kernel version 3.0.101, re-partitioned with Lanchons repit, and with recovery TWRP 3.1.0 installed and functioning.
I want to revert from CM13 to CM12.1. From above, I believe that I can simply backup, wipe, then flash the CM12.1 ROM (I'll be using the last nightly, cm-12.1-20160203-NIGHTLY-i9100.zip) - is that correct?
My question/confusion is, do I also need to flash an isorec-compatible kernel (ie kernel-Lanchon-TRIM-IsoRec-20160111-cm-12.1-i9100.zip)? The isorec thread (here) says that the "Official CyanogenMod 12.1 and 13 kernels are now IsoRec-compatible", so it seems to me unnecessary, but many threads/guides on XDA say to flash one of Lanchon's kernels.
Please could someone advise, and my apologies for what is probably an ignorant question.

 

[noppy22]

May I ask a supplementary question - I am in a similar position, I have an i9100 which I upgraded from stock 4.1.2 Jelly Bean to CM13 following (most of) djibe's guide here
So I now have CM13 ROM with kernel version 3.0.101, re-partitioned with Lanchons repit, and with recovery TWRP 3.1.0 installed and functioning.
I want to revert from CM13 to CM12.1. From above, I believe that I can simply backup, wipe, then flash the CM12.1 ROM (I'll be using the last nightly, cm-12.1-20160203-NIGHTLY-i9100.zip) - is that correct?
My question/confusion is, do I also need to flash an isorec-compatible kernel (ie kernel-Lanchon-TRIM-IsoRec-20160111-cm-12.1-i9100.zip)? The isorec thread (here) says that the "Official CyanogenMod 12.1 and 13 kernels are now IsoRec-compatible", so it seems to me unnecessary, but many threads/guides on XDA say to flash one of Lanchon's kernels.
Please could someone advise, and my apologies for what is probably an ignorant question.

You are correct. Isorec support was implemented before that last nightly iirc. No need to flash any kernels.

Note: Only use the official TWRP 3.1 from the TWRP website or the.gangster's one which is basically the same. They are compatible with the earlier android versions.

 

[teraghik]

Hi Noppy,
Thanks very much for taking the time to reply and help - I am using "the gangsters" TWRP 3.1 from djibe's thread, appreciate the heads up. I can confirm that I flashed CM12.1, and it works fine!

 

[djibe89]

Why don't you follow my tutorial to get the perfect smooth Android 7.1 for SGS2 ?
Here it is : https://xdaforums.com/galaxy-s2/help/guide-tutorial-samsung-galaxy-s2-i9100-t3538601