You cant, Unless you trade them all to your game, the only Pokemon Rio you can get in that game in Groudon, Kyogre, and Rayquaza
You only need to get all hoenn Pokemon to get johto starter It's a pain! :(
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.
You have to complete the Hoenn pokedex to get one from Prof. Birch. That includes catching all the Pokemon in there. This is impossible, but you can get a Johto starter if you finish your Hoenn pokedex and show it to professor Birch.
Gold silver and crystal but you can also get on emerald if you complete the hoenn dex. Also you can choose it as a starter in Soul Silver and Heart Gold
You can't get another starter Pokemon, once you have gotten one. The rarity of having a starter Pokemon, is that there is only one. You could trade with others to get the other starter Pokemon. But, with the Wireless Adapter thing.
Trade it from Sapphire, Ruby or Emerald.
Get a kanto starter :p
the 202 Pokemon in hoenn.
You cannot get a Yanma in Pokemon Emerald, as only Hoenn Region Pokemon can be found in Pokemon Emerald.
Get any Hoenn starter you want. It doesn't matter.
You are already there. Hoenn is the entire region in Pokemon Ruby/Sapphire/Emerald.
Regigigas is a Sinnoh pokemon. Not a Hoenn.