looks just like my 2 French Black Copper Marans and they hatched the 1st week of Jan....so they are now about 18 weeks old. they are both just as red and one of them is starting to squat. and she looks like a hen to me. i think it depends on the breed as to how quickly they mature.
I have seen and grown quite a few chicks and this looks like a Roo to me. What makes me think that this is a roo is first very red comb and wattles, 2. The curve at the end of the tail feathers, and 3rd size of the chicken is a bit larger than the other 2.
Make sure you keeps us posted!! If yours turns out to be a hen, then I have hope. My BA started growing wattles and comb at 4 weeks. When I posted pics, everyone said DEFINITELY roo! He hasn't crowed yet, so I guess we will both just wait and see