I don't know if the rules have been changed or not, but it used to be that in order to be in the August competition, the unit had to be released in August. I think the idea was to prevent people from submitting older, favorite units into the competition.
Yes you can, but ultimately it will be my decision...So, hypothetically, if I finish a unit at the end of August, I could conceivably enter it into the September Unit of the Month competition?