If you just startle the rat when it's asleep, it can be afraid and perhaps nip, but pet rats don't bite because of evilness. A tame rat will never bite, even if you put your finger in its mouth. Unfortunately only 1.5-3 years. Of course, that may not be so bad. If you get a dog or chinchilla you're bound to it for 15 years.
Females are usually more jumpy, while males prefer a life of leisure - on average.
There are always exceptions. There is really no difference in tameness. Fancy rats can be obtained from pet stores or from private breeders. When selecting, always choose the healthiest and the alertiest rat. It is best to get your pet rat around 4-8 weeks old.