Bloody Piercer / Tanya able to unlock? General questions/help

I'm not very familiar with the way this game works, i've only played a few days, and there really is not very much information in English for this game.

So, is it possible to get Tanya, with her Bloody Piercer? I don't know how to tell what characters are able to still be gotten.

Can I only get characters if I get their weapon from a draw? Or can I get characters from finding weapons on quests?