What if I don't have definite plan, should I put in a date sooner than later? Could I put undetermined?
Just put any reasonable date. It doesn't really matter. AP will be valid within one year of your approval date. Your specified date of departure has no influence here.
But make sure that you choose multi-entry
Part I item 3
Does "class of admissio mean my current Status, J1, or F2, etc?
It means the visa status when you entered USA.
Thanks!!