The first option is fine with me. The most important thing is to add the fic to the collection before the deadline, as the collection will be closed afterwards.

Generally speaking, I'd prefer the fics in the collection to be newly posted (i.e., reveals is the first time they are publicly available). That said, I don't mind giving an exception in cases like yours to accommodate multiple challenge dates.

Hope that helps clear things up, and let me know if you have any lingering questions!