Can I collect STAMP first and then claim if it reaches 30 STAMP?
Yes, you can stack up the STAMP. Later on, you need to click the "Claim Prize" button multiple times to claim the prize. Make sure you already collected the STAMP necessary to claim the prize on that day.
E.g.: You deliberately did not claim the prize on the 7th, 14th, and 22nd day because you wanted to claim the prize simultaneously on the 30th day. You can claim it that way by clicking the "Claim Prize" button multiple times. Please make sure you already checked in and collected the STAMP for 30 days. Also, you can only get one type of prize once.