Is possible to get early release from tcs if someone is on bench or do we have to serve notice period of 90 days?

Totally depends upon your RMG and HR. I am in a project, though I have no work assigne here and I got early release within 15 days of resignation, as I have buyout the NP.

So you can get early release if you are ready to pay the amount and your HR agrees to that.

Also, you can check with RMG if you're on bench, you might be released without any payment.

When on bench, you do not have to serve the 3 months notice period but as informed below it depends on your RMG HR too