 There is a lovely South American species of cat called a margay, which does live in trees, and its hind feet are double-jointed, so it can actually twist them around and point them backwards and walk down the street. But domestic cats have not figured that out. Well, they don't have those very adaptable ankles, so they're stuck with what they have. Yeah, they're going to get those ankles when they get the thumbs. A few hundred years. How could you do that?