Do all Levi 501's have button fly?

No, not all Levi's 501 jeans have a button fly. The classic Levi's 501 model traditionally features a button fly, but there are variations and newer styles, such as the Levi's 501 Skinny or 501 CT, which may come with a zipper fly. It's important to check the specific product details when purchasing to ensure you get the desired fly style.