Answer 1

There is no way to "resist" Gravity. This is because it is a field effect and not targeting your opponent. As such, the only way to stop Gravity is to stop your opponent from using it.

Answer 2

No, unless you use dive, dig, or bounce. Other wise you'll get hit every time

Comments

What about fly?

---

Fly doesn't work because it is negated by gravity.  The others are not a flying move and therefore, are not effected by gravity.  The only thing is that most flying types can't learn any of them.  Although, you can use moves like mirror move to get around that sometimes.

---

Bounce is also stopped by Gravity.