[Desire 820 Q&A, Help & Troubleshooting] alikhoshi:
Hi

Finally i flashed Lollipop on my d820 dual sim ( snapdragon ) and want to share my work.

It will not brick your device as i know but DO AT YOUR OWN RISK​

Requirements :

HTC Desire 820 Dual Sim ( a51-dtul ) Snapdragon 615 Chipset

S-OFF

Locked or Relocked Bootloader

India Stock 4.4.4 Rom ( has no Root access and never been rooted )

3 ROMS :

India 4.4.4 stock Backup :

https://mega.nz/#!7YJDFAbI!p0AVHYCe6JYZnsD9dac04eraDaNAFLkmc9xWXjlZ5FE

India Lollipop Rom (we need only 70MB firmware that included to it , i will upload it soon that you don't need download 990 MB :) ) :

http://144.76.118.99/direct-download-link/OTA_A51_DTUL_L50_DESIRE_SENSE60_MR_hTC_Asia_India_2.10.720.1_R-1.22.720.10_release_453049wea2pi2o56gw96qr.zip

India Lollipop Backup :

https://mega.nz/#!3M5AHRzL!haBZhbIBz4415rwYQVF9yR_g8WX-Tq_9rJHfCNTA6I8

At the first we have to flash or restore an Stock india 4.4.4 rom, if you have an India ROM installed no need to download first ROM at the top , if not you have to download that and restore with twrp recovery (Do Factory Reset After Restore) or Download RUU 4.4.4 India and flash it ( I Recommend this way ).

Now we have Stock 4.4.4 India installed

IMPORTANT :

Backup your rom with TWRP in external-sdcard ( don't backup to your phone storage , it will delete after re unlock bootloader and must push it with adb that is a hard way , so be carefull) , turn on your phone and put the 2nd downloaded file ( Extracted , not zip) in :

external-sdcard/TWRP/BACKUPS/"Your Phone ID"/"extracted folder"

Step 1 (Change CID to SuperCID) Must have S-OFF :

Go to Bootloader and select fastboot then try this commands :

1. "fastboot oem lock" to relock your bootloader

2. "fastboot reboot-bootloader" you can see your bootloader status is relocked.

3. "fastboot oem writecid 11111111" it will change your CID to SuperCID.

4. "fastboot reboot-bootloader"

after bootloader reboots you can see your CID that changed to "11111111".

Step 2 (flash firmware ( pre Lollipop 70MB update )) :

The downloaded zip file at second link that provide in top contains firmware.zip file , extract it from 990MB zip and put it to your fastboot folder.

Now we have to go in RUU mode :

"fastboot oem rebootRUU"

It will shows you an HTC silver logo that means your phone is ready to flash RUU.

Now flash the extracted firmware.zip using :

"fastboot flash zip firmware.zip"

It will take a while to flash this, if hangs let's try reflash it ( happens for me at the first time ).

After finished operation try this :

"fastboot reboot-bootloader"

Step 3 :

We have to restore our lollipop Rom :

The problem is firmware flashed stock recovery and we haven't TWRP. So you must unlock your bootloader again , after that flash twrp recovery with :

"fastboot flash recovery twrp.img"

Now go to restore section of TWRP , choose your sdcard to restore and restore the folder that pushed at the first in TWRP folder.

It will take a while so be patient , after installed finished do a factory reset then we have to go bootloader and re flash firmware.zip ( extracted from 990MB zip ) , the problem that happens for me is that i can't go to bootloader, the device everytime goes to recovery on boot :D , then no problem go to your TWRP and go restore section , select your backuped rom that create at the first and choose only it's boot section , no system , data or other , just select boot and restore it.

Now try this command in TWRP :

"adb reboot-bootloader" or you can manually reboot bootloader with TWRP reboot section.

At the end Do what you do in step 2 again after successfully install firmware you can use this command to reboot to system :

"fastboot reboot"

Wait your Lollipop Start :D:D

Enjoy :highfive:

Don't Forget Hit Thanks if it's useful for you​