This is a downgrade since the stable version is still using Android 10, you've to format the data partition before flashing stable release.
I've been using this stable release for 24 hours on Mi 9 lite, everything seems fine so far.
Just updated my Mi9 Lite from 11.0.4 (stable) to 12.0.2, seems everything went fine, thank you !
(OTA didn't work -> mirrors unavailable error, I just downloaded the firmware to the sdcard and updated from file)