Yes, You will be required to join allotted institution/college and complete the admission formalities. Only then can you exercise option to participate in second round and give willingness for upgradation at the allotted college, during admission process. If you wish to join and proceed for upgradation, then you will retain the seat incase you are not allotted any seat in round two. If you wish to leave the seat then, you will have 48 hours to do so, failing which you will be considered as joined. Then you will become ineligible to participate in any other counselling rounds.

Good Luck!