Hey Prakash
You need to go to SUIM t code as mentioned by Nishant.
For 1 and 2 you can check in SUIM as shown below it should give you a list of users etc .. in a system assigned to a particular role i.e 1 , 2 of your question ..
Point 3 , 4 are not that clear that is not something you check from roles I guess .. or maybe I am not understanding correctly .
Regards
Vinita