1) Is it ok to keep a kitten/cat at home?

2) What's the ruling about cats hair, according to Ayatullah Sistani?

3) Do we simply make sure to keep our Namaz Clothes, safe from the cats hair?

4) I think full black or full white cats are not recommended to have. Please clarify.

1) Yes. It is OK

2) One or two pieces does not harm the prayer

3) It is better to do so

4) No difference. You can adopt any color, even blue