nooooooooooooo!!
The odd opening position

xii only one with rook not on a8 =0
Again too complex. Keep these two things in mind:
1) Mathematical characteristic
2) 15 positions are IDENTICAL in one aspect

Dunno either, maybe all have the same number of moves?
Yes, this is it! No which one has more moves than the others?
is Queen's Gambit Declined one only one in D00-D99?
Yes it is, but it is waaay too complex for a question. Assume that the main question can be solved at a glance... If you look long enough.