^ but there is no ??? plate in the coding.
anyways
hidden power is a move that changes its type according the the IV's of the pokemon, its maximum power is 70 i believe, it can be any type excluding ??? and normal.
its only really helpful if you want to add type coverage, but the pokemon you are teaching doesnt have a good move in that type, but can achieve a high power HP in that type.
i hope this helps.
oh also, you can test out what your HP is, just use it on a pokemon, see what its effectiveness is, and go try it on a differant type of pokemon, your HP type and power will stay the same for that pokemon no matter what