1. I have done a some Free Flight to explore it again and first thing I encounter is, that the cannon no longer auto-aim…
Not exactly sure what you mean by auto-aim. Depending on the cannontracking setting in eech.ini and the current targeting system it's either going to follow your head, the targeting system (TADS, radar), or fire straight ahead.
3. And the doors are now closed before motor-start, it looked nice to see them close.
If you set enginestartup to 1 in eech.ini they will start open (but you will then also have to start the engines yourself). And you can of course open them yourself with ALT+C.