Minecraft number of active users

Might want to get into contact with Mojang as they will be the best place to get this sort of information.

I suggest you to post this question at the game developers forums in order to get a proper answer as their info would be up to date.

That is a strange one! I guess it would be different from game to game, but you would think that if you are assigned to the controller, and signed in, then providing you are using that controller you would remain signed in no matter what game or application
you were using.

Quitting out of the app or game should prevent the 'pushing b' issue, so when he is done with the game, highlight the tile, hit the menu button, then select 'quit game'. That should prevent you accidently hitting b and going back into it. I do this for all
games, I never leave them running in the background, is just a personal habit

You have me stumped sorry, hopefully someone else may be able to give you some further tips

You have a couple of options

If you're using different controllers, then the easiest way would be to assign a profile to the controller:

support.xbox.com/.../assign-controller-profile

To switch profiles, follow these steps:
support.xbox.com/.../switch-profiles

And you can check which profile is signed in, up in the top left corner of the screen. It should be displaying your profile

Yes, that is correct and how I use it.

The issue is with the ACTIVE application. If I use my voice to go to my stuff and then run the same game that my kid was using then I continue playing with his user not mine

The same happens if I go to my user and then press B. It goes to the last app but if the last app was running with my sons account then it continues that way. And as far as I was able to see not all games shows you wich user is active.