Next era of games is not VR. But will UE capable? Ideas of your old fan from 1999.

Yes… The engine is quite capable.

Not entirely sure, for I do not mess with any multiplayer.
But it’s most likely possible, all you need is some good coders. And at worst to mess with the source code.

This is entirely up to the game developer to add realism or not. (Well… Up to engine limitations of course.)

Once again, This is up to the Developer. It can be done fine in UE4.

This is once again up to the Dev, the engine does this fine.