
You can resume playing your GBA game with this save, and you could also play the NDS game on an emulator if you wanted, but most likely you'd rather play on your DS, and the only way to make use of the save file your buddy sent you is using a flash card (to either write the save to the original game, or just along with a ROM of the game). The GBA save will be less your Pokémon presumably (honestly I haven't played one of these things since Silver, so I don't know the exact process of trading between generations), while the NDS save will have them. They can transfer your Pokémon across, and then send you both (GBA and NDS) save files. They can write the (GBA) save file to their (SLOT-2) flash cart and run Pokémon Platinum (patched for SLOT-2 cart save reading assuming this patch exists, as it does for Diamond and Pearl) on their SLOT-1 card. If you don't have both of those, you could instead send your (GBA) save file to someone who does.


Well basically, the process involves a SLOT-1 card and a SLOT-2 cart.
