First you beat Elite Four. Then go to Snowpoint City. Talk to the guy with the boat, He'll ask you which island you want to go to.
You get the Rainbow Pass from Bill in order to have access to the other four islands in the sevii islands.
Manaphy cannot take you to other islands - manaphy is just another Pokemon.
You go to the other islands.
The Orange Islands do not exist in any Pokemon game.
The Sea Foam Islands are not in Pokemon Ruby.
Not regions seen in other games, but you can visit some islands that are introduced in the FireRed and LeafGreen games.
The orange islands are made up islands strictly used for the Pokemon cartoon.
Cinnibar island, Fuschia city, the Pokemon league and two island and the other islands.
The Sevii Islands are a fictional archipelago of nine large islands and several small islands surrounding them. They are far south of Kanto, and are home to several legendary Pokemon. They appear in Pokemon LeafGreen and FireRed, and peripherally in Pokemon Emerald.
Get the national dex go to mt ember and get the ruby take it to celio and you will get the rainbow pass this gives you access to the rest of the islands.
No legendary resides on the islands a rare Pokemon resides on seven island in the tanoby chambers the Pokemon is unown.
Explore, catch pokemon, train your pokemon.