I would say Hen, the Hackle feathers are not very long or pointy...and by this time I am sure you would have heard crowing if it were a Roo...unless you have one Shy roo!
I'm not sure of it's age, I have some other chickens that I know are 4 months, dominiques and cuckoo marans, that are much smaller, so I was just making a guess by comparing size. It seems to grow a lot almost daily