It’s normally used in an exaggerated tone. So if someone has has very long nails they might be referred to as claws. Or someone might say “hey, get your claws off of me!” Which means take your hands off of me/ let go of me.

Yes absolutely though it's a little strange in casual conversation.

No, claws are specifically for animals.

Yes. It would be used as a metaphor. This means that while you wouldn't normally call fingernails claws, you might do it to exaggerate and compare the size of someone's fingernails to the large claws of an animal, or perhaps to express the idea that someone may have captured or restrained someone else by getting their imaginary claws into them. I realise that Tatum did give a good response but I just wanted to introduce the idea of saying something metaphorically. In English we have two similar types of "figure of speech": the simile, and the metaphor. A simile would say "her fingernails are like claws." A metaphor would say "her fingernails are claws." Both are intended as a description of fingernails, and the word claws does not get used as an alternative to fingernails unless you intend to make this exaggerated comparison between the fingernails and claws.

Well—actually, “some” of the “ladies” in the Deep South—myself included— do indeed use the term “claws” to describe the manicure of other “Southern Belles.” But, this is a very “catty” (yes, pun intended!) way to refer to a “lady” and is usually used in a sarcastic or passive-aggressive fashion. Alas—one must delve deep into the psyche of Southern Ladyhood to even begin to comprehend our mysterious and often mischievous ways...”Bless yore heart!”.....