[Desire 626 General] hp79:
Reasons to go back

- SIM Unlock tool doesn't work in Marshmallow (The SIM unlock app has a bug)

- Want to check out custom ROMs built on Lollipop

- Just because you can

Once you take the OS update to Marshmallow either through OTA or RUU exe file from HTC website, you can't go back to previous versions of the OS. This is because the misc partition keeps a copy of the version number and if the RUU you want to install is lower than that of what your phone has, it'll stop upgrading.

This is a big problem especially if you haven't SIM unlocked your MetroPCS HTC 626s yet, but upgraded the OS, and the current MetroPCS SIM unlock tool doesn't work. I was stuck in this situation without knowing what the cause was and wasted so much time. I called customer support several times, visited MetroPCS stores twice, all they could offer me was a replacement to a refurbished device and $20 out of pocket.

Instruction

Anyways, assuming you are on on Marshmallow (2.17.1550.1) the procedure to go back to Lollipop (1.23.1550.3) is the following:

1. Install TWRP for a32e. This is done in download mode through "fastboot flash recovery [twrpimage.img]" command.

https://twrp.me/devices/htcdesire626s.html

2. Install SuperSU 2.78 zip file inside TWRP recovery menu. Download the file, copy it in to your phone, reboot to recovery mode to TWRP, install the zip from there.

http://xdaforums.com/apps/supersu/stable-2016-09-01supersu-v2-78-release-t3452703

3. Restore the edited misc.img to your phone's partition. You can use my misc.img file attached in this thread. I only changed the version number from 2.17.1550.1 to 1.00.0000.0 using a hex editor. I compressed the misc.img file, so extract this file before proceeding.

http://xdaforums.com/attachment.php?attachmentid=3873126&stc=1&d=1473705500

You can do:

"adb push misc.img /sdcard/".

"adb shell"

"su"

"dd if=/sdcard/misc.img of=/dev/block/bootdevice/by-name/misc"

These commands will overwrite your misc partition so that the main version is set to 1.00.0000.0. This allows the lower version Lollipop RUU to be installed.

There's no need to reboot. Just run the Lollipop RUU exe and let it reinstall the stock ROM and you are done.

After all this you can run the MetroPCS SIM unlock app, and it'll work properly and let you permanent SIM unlock as long as you are eligible (after 90 days of service).

Stock RUU downloads:

Marshmallow 2.17.1550.1 Stock RUU exe from HTC.com:

http://dl3.htc.com/application/RUU_A32E_UL_M60_DESIRE_SENSE70_MR_MetroPCS_US_2.17.1550.1.exe

Lollipop 1.23.1550.3 Stock RUU exe from HTC.com:

http://dl3.htc.com/application/RUU_A32E_UL_L51_DESIRE_SENSE70_MetroPCS_US_1.23.1550.3.exe

Credits

Big thanks and credit to: [MENTION=2900755]GotHeart[/MENTION] [MENTION=7006025]BigCountry907[/MENTION]

I posted this write-up since I have just recently gone through the process.

Other details, but not needed for performing the job here:

I tried mainver changing tools from old threads, but they didn't work.

To backup your misc partition in case you want to edit it yourself:

"dd if=/dev/block/bootdevice/by-name/misc of=/sdcard/misc.img"

Then bring the misc.img file to a computer and use any hex editor and look for the version number 2.17.1550.1 if you have the current Marshmallow, change it to 1.00.0000.0. That is the attached misc.img file in this thread.

Update: There is an update to this version ROM which is 2.17.1550.13. I don't know what changes there were from 2.17.1550.1 but hey it's something. I'm going to install the update and then root again. It might be a fix with the broken MetroPCS SIM Unlock app, but I don't know as mine is already SIM unlocked.

edit on 7/25/2017--

Latest version stock ROM as of 7/25/2017

Marshmallow 2.17.1550.23 Stock RUU exe from HTC.com

I had to redo all the flash recovery parition to install teamwin and install SuperSU, but after everything root is working fine.