If I resign on monday, how many notice period I have to serve, I'm on bench from 1st July

3 days to 7 days

On the bench you don't need to stay 90 days..

It depends if you release from project then its less than 10 days if you got offer you need to push HR for immediate release. if you tagged to project then it depends upon manager and work complexity. If manager is good then i seen many people got released in 1 month.

Did HR asked you to resign

You can rt away in a week