Do cats have 7 or 9 lives?

That's simply a difference in culture. In some areas of the world, the "magical number" is seven, in others is nine. Of course in both cases the answer is no, they just have incredibly good luck and an innate ability to cheat death with their agility. They tend to be resilient in situations that most animals would not be so.
Cats can survive falls from high places with few, if any injuries. This gives the appearance that the cats return to life after sustaining a fatal accidents.