Most of those questions can be answered from reading the manual.
In order of the questions, rule <G29>,
There is no rule saying you can’t,
Rule <G12> and <G13>,
and finally just look at the Possessions Definition for the last question.
for the first one I am not sure, I think you can but you would be scoring for them so thats not so smart
Yes, you can pass the ball over the center divide, but that seems like a lot of work to do,
And you only score points for having both the robot and the ball cross YOUR finish line, not both (the only time you get points for scoring through their finish line is in hybrid mode,
And finally, I think blocking their ball is probally illegal and stupid because if your blocking their ball then you cant be scoring!