Hello Guru,
Well yes, if you want to secure your allotted seat in first round and want to participate in second round you have to visit the college and apply for upgradation.
If you do not do so, your earlier allotted seat will not be secured and you will lose that seat of yours.
If you do not get a seat in second round you can still take admission in the earlier allotted seat if you have visited that earlier i.e. at the time of first round of counseling.
I hope this helps.
All the best for the future!!