A few answers
- anbox is very experimental still so personally I would expect more than 50% of all apps to not work (anything that uses Google services like the maps api will not work); and probably less than 10% of apps to work without major issues (for me, of around 12 apps I tried only spotify works without me noticing problems)
- as far as I know there is no icon for anbox (it's just software that runs in the background)
- I guess these are system apps (on a normal android they are not listed by default in the settings apps)
- after you enabled anbox with anbox-tool it is supposed to start automatically on boot, but if I remember correctly I also had situations were some commands didn't work; only after starting an android app those were possible so I guess there is still some difference between something like "ready" and "running" or so (or maybe it's just a bug due to the experimental nature of anbox on UT)
- Android apps rely on a back button, so running android apps on a system that doesn't have those just can't be operated fully; there may or not be workarounds like stopping the app and starting it again