Is it still rolling upgrade from 20.2.4 to 20.3?
 

The Deepin 20.3 has been released for 3 or more weeks. My Deepin keeps popping up a message "new system editions available". The latest version hasn't been installed though. Does the version still do the rolling upgrade or do I have to do manual installation? I installed the 20.2 version initially. And its rolling upgrade updated the consequent releases automatically before the 20.3 version.

yes

To my experience up today, it doesn't do rolling upgrade. I have to run something like 'sudo apt get dist-upgrade".

 

The terms "rolling release" and "automatic upgrade" are two different things.

According to Distrowatch, Deepin is not a rolling release any more (but it was until 2016).

For automatic upgrades, there's probably an explanation on the Deepin Wiki, but I don't know Chinese so can't confirm.
(If there isn't, the Debian wiki has a page and probably works the same for Deepin.)

Luckily, they have translated Package Management into English.