No, a mule or a hinny are both hybrids. A mule is a cross between a male donkey and a female horse and a hinny is a cross between a male horse and a female donkey. Both are sterile, a mare mule or hinny will still have a heat cycle but the reproductive parts inside do not work so even if you bred them they would not have a foal. It has happened on rare occasions though.
I believe all mules are sterile. It's probably not possible
Hinnies and mules are sterile and cannot breed. The only way to get either is to breed a horse and a donkey together. If the father is a donkey, I think you get a mule. If the father is the horse then you get a hinny.