bonita 7.4.1

How to redirect from one page to another with different log in user, how change the current log in user through process?

I have been trying implement a simple request application where user can log in and make a request to admin. And admin can approve that request or can reject that request. But when i create a log in process I am not able to log in with different user it will only keep log in the process initiator.
Also i am not understanding hi i am going to change the request form on base of user role means after log in i have to show the forms as per the user role. But i am not able to do that.