New Android 5 lollipop firmware is available for download for the K2 S812 android TV. It is on sale for about 80 euro from various online websites. The K2 S812 makes use of Amlogic SoC and it is easy to download and flash the lollipop Android 5.1 firmware on it. Here is how you do it. You can also use this method to factory reset K2 S812.
How to flash the Android 5 Lollipop for K2 S812 Android TV
Download the firmware from here. To update, you must unzip the file you downloaded and copy it to the root of Micro SD card:
Insert the card into the TV-Box K2. Go to the System Update option. Find it in Settings and press SELECT, select Wipe Data and Wipe Media. Click Update.
The computer will automatically update and restart at the end. Do not touch the TV-Box under this process.