Welcome your new Android (Lollipop)
How to install Lollipop Update on HTC Desire 820 Dual SIM
The Easy & Traditional Way
1. Stock recovery
2. Stable Internet Connection
3. At least 50% Battery
Disclaimer : Make sure you have not modified any system files for eg :- platform.xml for getting SD card write permissions.
How to get Lollipop Running :-
1. Connect your phone to Internet (WiFi recommended)
2. Goto Settings -> About -> Software Updates
3. Install OTA update for Kitkat (70mb approx).
4. After installation has finished your phone will restart.
5. Again check for updates, this time it will show Lollipop update (990 mb approx).
6. Wait for downloading to finish, wait until it verifies update package.
7. A popup will open select Install Now and press OK.
8. It will take around 20-30 minutes to complete.
9. Holla, now you have Lollipop running.