//EDIT// If you like, you can try simply flashing the firmware listed below in post #2. For most folks, this will work. If it doesn't, use the comprehensive steps I listed below.
Why?
There have been several folks in the CM11 thread asking how to downgrade from 2.16. This thread is simply a repost from the reply I made over there for ready reference.
Note: This is for T-Mobile US users only, but should work for all, as long as you use the appropriate RUU and CID.
Also, you will need the ability to use fastboot commands. Windows 8.1 will not work. I know fastboot works with Win8.1 on other phones and devices, but it doesn't as of now for the Ville.
Well, this is what I did and it worked fine (backing up SD card, of course):
Steps
1) Undo SuperCID (if you did), changing it to TMOUS10
2) Lock bootloader (fastboot oem lock)
3) Run RUU, I used RUU_Ville_U_JB_45_S_TMOUS_3.14.531.11_Radio_1.13.5 0.05.31_10.30.50.08L_release_309489_signed_ICS_2
4) Verify S-Off is still there (it was for me). If it's not, then achieve S-Off again if you want it.
5) Unlock bootloader using HTC Dev
6) Fastboot flash recovery (I used the latest TWRP that had been modified for SELinux, available in the CM11 thread)
Note-- I did get an encrypted SD-Card error prompting me for a password the first time I booted into TWRP-- simply wiping all partitions and rebooting back into recovery fixed this
7) Install CM11, gapps, etc.
8) Install latest radio, 1.20-- available from the radio update thread
Other notes/explanations
A number of threads, both here and Evita, warned against flashing a RUU on CID 11111111, which is what I had. It seems some folks change it back, some don't, but it wasn't worth the risk of a brick for me.
You'll note the RUU I used is NOT the latest available from TMobile/HTC, as I wasn't sure if it was S-Off capable, and again did not want to add extra steps or lose S-Off.
I didn't bother restoring the data partition or converting back to superCID, as I kept my S-Off, and didn't see any value to either.
A few random folks seem to have lost 3G/4G after downgrading to 2.15, but I didn't. If you do, please post here.
Why?
There have been several folks in the CM11 thread asking how to downgrade from 2.16. This thread is simply a repost from the reply I made over there for ready reference.
Note: This is for T-Mobile US users only, but should work for all, as long as you use the appropriate RUU and CID.
Also, you will need the ability to use fastboot commands. Windows 8.1 will not work. I know fastboot works with Win8.1 on other phones and devices, but it doesn't as of now for the Ville.
Well, this is what I did and it worked fine (backing up SD card, of course):
Steps
1) Undo SuperCID (if you did), changing it to TMOUS10
2) Lock bootloader (fastboot oem lock)
3) Run RUU, I used RUU_Ville_U_JB_45_S_TMOUS_3.14.531.11_Radio_1.13.5 0.05.31_10.30.50.08L_release_309489_signed_ICS_2
4) Verify S-Off is still there (it was for me). If it's not, then achieve S-Off again if you want it.
5) Unlock bootloader using HTC Dev
6) Fastboot flash recovery (I used the latest TWRP that had been modified for SELinux, available in the CM11 thread)
Note-- I did get an encrypted SD-Card error prompting me for a password the first time I booted into TWRP-- simply wiping all partitions and rebooting back into recovery fixed this
7) Install CM11, gapps, etc.
8) Install latest radio, 1.20-- available from the radio update thread
Other notes/explanations
A number of threads, both here and Evita, warned against flashing a RUU on CID 11111111, which is what I had. It seems some folks change it back, some don't, but it wasn't worth the risk of a brick for me.
You'll note the RUU I used is NOT the latest available from TMobile/HTC, as I wasn't sure if it was S-Off capable, and again did not want to add extra steps or lose S-Off.
I didn't bother restoring the data partition or converting back to superCID, as I kept my S-Off, and didn't see any value to either.
A few random folks seem to have lost 3G/4G after downgrading to 2.15, but I didn't. If you do, please post here.