Cats are permissible to have, but it is not allowed to pray with cat hair on ones clothes. This is because, even though being Tahir, we are not allowed to pray with fur from an animal that is forbidden to eat.
Yes their urine and excretion is najas
To clean urine you must was with water twice when using leas than Kurr water or either once with Kurr water or something connected to kurr water
Excretion needs to be cleaned with water once.