It is in a house next to a Pokémon center, in Blakthorn City.
you go to blackhorn city and there you will find a place there
in blackthorn city there is a house full of people that can teach moves to pokemon, make pokemon forget moves etc;
There's a move deleter in blackthorn city he can remove hm moves.
There is a move deleter who can make pokemon forget HM moves.
Yes you can trade them over but they won't be able to forget the HM moves until you find the move deleter.
mewto
hydro pump, hydro cannon and two defensive moves.
Use a spooky plate.
goldenrod and celadon department store.
Whatever you teach it! :D
You need the Pokeflute, but I forget where it is.
you have to get to blackthorn city first