because even with a yellow book you could still go somewhere else to stay, like a hotel etc and they'd do a TM30. So that's what's relevant. The TM30 says where your physical body is staying.
VOA is 15 days. You buy it at airport when you enter. But only certain countries do that. You've probably entered without a visa, on the 60 days exempt. Can go to immigration and extend it for 30 days.