Professor Elm will give you HM Rock Climb after the 16 badge.I think after you have collected all 16 badges you can talk to prof. elm and he will give it you.
It's not the "last" Legendary Pokemon that you can find in Pokemon HeartGold, but most people usually catch that one last given that you need to have both Kyogre and Groudon in your party for Professor Oak to give you the Jade Orb to get to Rayquaza.
he will give you the national pokedex then when you go to kanto he's in pallet town in his lab
After catching Kyogre, obtain a Groudon from a friend with Pokemon SoulSilver. You only need the Groudon temporarily. Talk to Professor Oak with both in your party, and Professor Oak will give you the Jade Orb to catch Raquayza.
He gives you the HM Rock Climb, and if you also defeat Red, you can get one of the Kanto Starter Pokemon.
after you beat all the gym leaders in kanto and johto reigons he calls you to say that he forgot to give you something so you go to pallet town and he will give you rock climb.
Beat all The Johto and Kanto Gym Battles and then speak with Professor Oak and he will give it to you.
Afterwards, Professor Oak will give you a Generation 1 starter (Bulbasaur, Charmander, or Squirtle)
Professor Elm will give you HM Rock Climb after the 16 badge.I think after you have collected all 16 badges you can talk to prof. elm and he will give it you.
You do not need to show Rayquaza to anyone in HeartGold. In order to get Rayquaza, you need to show Kyogre and Groudon (from HeartGold and SoulSilver) to Professor Oak. In turn, he will give you the Green Orb. With the Green Orb in hand, you can find Rayquaza in the Embedded Tower.
you get it after you get all 8 gym badges from Johto and Kanto. Once you defeated the last one in Kanto, Professor Oak will call saying he has something for you. Go to him and he'll give you Rock Climb
It's not the "last" Legendary Pokemon that you can find in Pokemon HeartGold, but most people usually catch that one last given that you need to have both Kyogre and Groudon in your party for Professor Oak to give you the Jade Orb to get to Rayquaza.
he will give you the national pokedex then when you go to kanto he's in pallet town in his lab
After catching Kyogre, obtain a Groudon from a friend with Pokemon SoulSilver. You only need the Groudon temporarily. Talk to Professor Oak with both in your party, and Professor Oak will give you the Jade Orb to catch Raquayza.
After you defeat the main 8 gyms professor oak will call you to his lab and say he has something for you. Then he will give you a master ball.
He gives you the HM Rock Climb, and if you also defeat Red, you can get one of the Kanto Starter Pokemon.
In Pokemon Emerald, when you complete the Hoenn Pokedex, Proffesor Birch gives you a Johto starter. In Pokemon HeartGold and SoulSilver, after defeating Red, Professor Oak will give you a Kanto Starter and Steven will give you a Hoenn Starter.