I have a couple of questions. 1: How do you access islands 4-8?

Sorry to any of you who went searching for answers to the preceeding question, here are the ones I found after posting it.

Islands 4-7 can only be reached after you defeat the Pokemon League. They are accessed after you talk to Oak and he tells you about the outbreak of Johto Pokemon in the archipelago (I believe this is after you catch all of the legendary birds, but it could also have to do with the amount of pokemon you've caught). From that point sail to One Island and head up Kindle Road to Mt. Ember.

Once you reach it take the first turn east and drive away the rockets who just finished excavating, then follow the cave's path untill you reach a fork. At this point turn west and you will soon reach a chamber with a ruby at its center and a note in braille on the northern wall (the note reads "everything has meaning existence, has meaning being alive, has meaning have dreams use power").

Retrieve the ruby and head back the center, then give it to Celio and he will tell you to go retrieve the sapphire residing on Six Island and give you a Rainbow Pass. Sail to Four Island and help Lorielli kick the rockets out of Icefall Cave, then head to Six Island and down Water Path to Ruin Valley. Circle around untill you reach the Dotted Hole (described by others in the valley as the "Mysterious Ruins") and use cut in front of the entrance.

Once you get inside, drop through the series of holes and you will reach the sapphire (to do this follow the directions of "up", "right", and "down" to descend-if you don't, you will end up back on the floor you enter through). However, just as you are about to retrieve the stone, a scientist drops in and steals it from you. After he leaves, exit and head to Five Island (there is also a notice in the sapphire chamber which reads "let the two glittering stones, one in red, one in blue, connect the past; two friends sharing power open a window to a new world that glows. the next world waits for you").

When you reach Five Island follow the sandbar east and head through the meadow untill you reach the rocket warehouse. Enter the two passwords you obtained from the people near/in the ruby and sapphire chambers, then fight your way through and drive the rockets out. Once you do, head up and fight the scientist who stole the sapphire, and once you defeat him and get it back return to One Island.

Hand the sapphire to Celio and he will add it to the machine, enabling you to trade with the Ruby/Sapphire versions. When you reach the mainland, you should also be able to enter Cerulean Cave (it is possible that you need to do something else such as opening the Tanobe Ruins to access the cave, but I highly doubt it).

ISLANDS 1-3 are accessable BEFORE you beat the elite 4. 4-7 are only accessable after you beat the elite 4, and have at least sixty Pokemon in your pokedex. I think you are able to go to cerulean after you get the ruby and sapphire so you are able to trade.