I'm having some issues with a kitten (~8 weeks old) I'm fostering. Sorry if my formatting sucks, I'm on mobile.

1) She's super sweet, but she can sometimes play too rough. My cats are starting to warm up to the kitten so they're playing a little bit but not very active (wrestling, running around). So when i play with her, she'll bite and scratch my hands and arms really hard.

2) She's inconsistent with the litter box. She goes to the box to poop I've seen her do it a few times and see her mini turds in the box when i scoop, but she pees pretty much anywhere she wants. So it's not that she doesn't know where the box is or how to use it.

I'm assuming the first problem is lack of interaction with other kittens? She was found abandoned by herself, no littermates or mom in the area. The second problem, I'm at a loss. Is this something mom teaches the kittens? What can I do?