If the dog has not been spayed or neutered, then yes, it is possible to breed it. But it would be highly discouraged to breed any dog that has such a physical abnormality. The genetics that caused the underbite in your dog could easily be passed on to the resulting puppies.
Yes, they do have an under bite, where the lower jaw protrudes somewhat beyond the upper jaw.
No, but some are born and supposed to have under bites.
boxer dogs
Boxer dogs. You better belive it.
Australian Shepherds, Shih-Tzus, and Miniature Schnauzers mostly have under bites. There's nothing wrong with it. Their lower jaw is just larger than the top jaw. They're born that way
Because they're dogs...
They can be if you train them the right way.
A boxer dog is a jogger because it is a submissive dog.
Food
They have no predators
No
water.
Around two months the same as dogs that are not inbreed dogs