The elemental hyper beams for the starters(hydro cannon, blast burn, and frenzy plant) are not in emerald. So, the only way you can get a Pokemon in emerald with these moves is to trade it to FR/LG and go to Cape Brink. Although, it can only be taught to Venusaur, Charizard or Blastiose and can be used once, so if youre trying to teach a 3rd gen starter the move, you are out of luck.
Source: http://bulbapedia.bulbagarden.net/wiki/Move_tutor
