If you mistakenly selected float in UPTAC Round 2 instead of freeze, it means you're still in the race for better options, and your Round 2 seat isn't confirmed. To try and get that same seat again in Round 3, you should put that same college and branch as your first preference during choice filling. However, there's no guarantee that the same seat will be allotted again, as it depends on seat availability and other candidates choices. So act quickly and fill your preferences carefully in the next round.