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I've played FireRed on Gameboy Advance, saves it, and then resume playing on the DS, migrate some pokemons and it's fine.
I just purchased 3 used Gameboy (Leafgreen, sapphire & emerald). I played it on the GBAdv, saved the game. Then my sister tried to play it on her DS. She put the game in the GBslot of her DS, turns on the DS, sees "DS game" or "Gameboy game". She selected "Gameboy game" to check that the GBgame saved info/file was there. It was. Then she turned it off. Turn DS back on to select "DS game". She sees that "migrate pokemon" is not there. So she turns it off. Then on again, selecting "GB game" again and see that the saved info/file is not there anymore. We didn't get that problem on the FireRed.
We tried it on all the 3 games we bought & the same thing happens.
We just want to double check before returning the games. I don't think it's suppose to happen (even though these are older games?). Is it suppose to happen? We should be able to migrate and save game files and play the game between GB and DS (as with FireRed with success). Let us know. Thanks.