Hello Deependra

Yes you can  withdraw if you withdraw from JOSAA , your fees will  be refunded after a deduction of Rs. 1500/- as the procedural fees.

Seat Withdraw Process works as follows:

• Candidates who have already accepted a seat, can only withdraw the accepted seat by coming to the reporting center before the last round.
• After withdrawing, the candidate will not be allowed to participate in any more rounds.
• Students can not withdraw the seats after the announcement of last round of  seat allocation.
• The letter should be duly signed by the candidates and their parents and have to report to the reporting center for withdrawing procedure.
• You are only allowed to withdraw till 6th round.

Yes after withdrawing you can take a drop year and prepare for JEE and come out it with even better rank

hope this helps you