@lodhi Please note going back and forth from 20.04 to 16.04 may throw up some issues. Treat them as 2 different OS. The apps can be completly different as is the OpenStore the main idea is that when you move you stay there.
My 3a had a few issues with installing after a few back and forths. There will be another RC soon for 20.04 and I would recommend that for the 3a which runs great on 20.04.