Hello Mounisha,
You have not specified your state, so talking generally under All India Quota, if you have got seat after second round of counselling or mop up round of counselling, then your security money will not be refunded that means it will be forfeited. If you have got seat under first round of counselling, then you can exit and not report to your alloted college, you will get your security money back. Registration amount is not refundable in any case.
Hope this helps you.