They have what is called a labyrinth organ. They can survive for several hours out of the water, but I don't think any of us want that for our pet until he can be discovered.
Rocks are optional.
A 100 percent water change will not hurt them. As with any animal, their urine produces ammonia, and if the water is left unchanged, it will poison the fish. I want to show them off, not make excuses for their dirty water. They all work the same way. They like the salt and it helps to fight disease.