I've never flown Frontier before, though will be doing so for the first time next week as part of an Apple Vacations charter from ORD-CUN. So a few questions.

(1) My flight departs ORD at 6:00 a.m. Can I check-in online prior to or do I have to show up at the counter at 4:00 a.m. (or earlier)? Since this is an international flight, is online check-in even an option?

(2) I can log into my reservation on Frontier's web site. I can currently buy stretch seats for $45 each (there are two of us) for each flight. Are the seats worth the upcharge?

3) I notice in Rows 10 and 26, that there are only 2 seats on each side of the aisle, while all of the other rows have 3 seats on each side. Are these ideal, since my wife and I wouldn't have someone in the row with us, or is there a disadvantage to these seats?

Your assistance is appreciated. I typically fly United and AA, so this is all new to me.

PTEM