Sure can. I have done it several times. Usually when I forgot to take out the meat before I left for work. If you plan on frying it though you must defrost it first.

My cat has had a few litters she goes out shortly after she has had them but always wants right back in. As long as you have a way to let her in and out easy she can go out whenever she wants.

You can give them away at 6 weeks but it is best to wait till they are at least 8 weeks. They are completely weened at that point and wont be as likely to try and suckle on their new owner.