On your watch, Go to menu, settings, system, about. It will tell you what version is on your watch.
I think I might have figured out what's going on, but I'm hoping someone can validate my suspicion. Prior to receiving my 235, I was using the VSHR. In Garmin Express I checked "never" under automatically update my device. Is it possible that Garmin Express only downloaded v3.20 to my watch and "thinks" that I'm running that version even though I never manually installed it on my watch?
On your watch, Go to menu, settings, system, about. It will tell you what version is on your watch.
If you connect the watch to a computer, have a look in the GARMIN folder. If there is a firmware update pending you should see a GUPDATE.GCD file.
You may also see other files in REMOTESW which are typically software components like the sensor hub.
On that, AFAIK it was the update to the sensor hub that changed 24x7 behaviour not the 3.10-3.20 update.