Hi, 

If you don't get a seat in the first round then you can apply for second round counselling.

You will have to fill in fresh choices and go through the whole counselling procedure. If after allotment you get a seat then you will have to go and do admission in the college. There is no scope of free exit in round 2.

However if you still dont get a seat in round 2 then you can also participate in mopup round counselling. Usually chances are little better in this round.

All the best