couple of quesitons

[Cuno03]

Hey everyone...sorry if these has been asked before....

Once you get to the Islands, how can you go back to Kanto?

Are both Japanese and English versions of the game compatible with each other? (as in I have the Japanese version and want to battle with someone who has English)

Thanks in advance!

[Don't Run With Scizors]

Yup, they are.

[Orion]

To get back to Kanto, I think you must do all the mini-quests available at the moment (Save the girl from the Hypno, defeat the Bike Gang in Island 3.). Not sure if it's necessary, though. Either way, just talk with the scientist that's with Bill in Island 1's Pokémon Center (Near the big Machine.). After some talk, you'll be taken back to Cinnabar. If you wanna go back to the Islands, go to Vermilion City, to where the S.S. Anne used to be. The sailor there will take you to the Islands whenever you want.

[Moonlight Espeon]

Okay, I'll explain a few things that I don't know if you need to know or not, but....
First, you get taken to the Islands Three after defeating Blaine at Cinnabar. After you complete the quests (Go to Pokemon Center on One Island and talk to Celio, go to Two Island, save the girl from the Hypno, defeat Biker Gang on Three Island. After doing all of this, fly back to One Island and speak to Bill in the Pokemon Center, you'll get taken back to Cinnabar. You'll be given a Tri-Pass before this, to use it go to Vermillion and you can sail to the Islands again.