how and when do silkies age?

[L*A*G*]

i pick up four 3 weeks old silkies tomarrow.
what will they look like?
also tell me about how and how old when hens and roosters age as they grow.
since i'm not good at explaining this is for example.


hens:
so &so age when loose chick feathers...
and so on about diferent things


roos:
so & so age when crow...
and so on about diferent things