You have to deposit counselling participation fee. Only after this you can register for IPU CET Counselling. After choice filling, you will be allotted seats as per merit.
If any seat is allotted, you have to pay academic fee, if not paid you will not be considered for subsequent rounds. If you withdraw the admission, you will be eligible only for spot round.
Once allotted a seat, if you do not want to participate in next rounds you can freeze it. If you do not freeze the allotted seat, the next higher preference may be allotted in next rounds.