Are 2nd hand car seats ok? Or how old a car seat is still ok? I know car seats and cribs get recalled to stay updated with safety standards

You're right in saying that things like this get recalled pretty often to meet new standards. In light of that, I'd advise just buying a new car seat. Safety isn't one of those things parents should be frugal with. You can be frugal when it comes to other purchases but, you may want to just play it safe with a car seat.