That is possible.
Yes.
FYI.....semantics, maybe, but can be important communication terms when discussing chicken behavior.
Female chickens are called pullets until one year of age, then they are called hens.
Male chickens are called cockerels until one year of age, then they are called...
They always were cockerels ;)
How old are they?
Depends on their demeanor's and the amount of space you have.
I would not keep more than one male, no need for it.