I have a Game Boy Advance SP and Pokemon Red GEN 1, and I'm curious if it is possible for me to trade a Pokemon from Red to the Virtual Console release of Pokemon Gold on the 3DS
You can't trade from a cartridge to a 3DS console.
But there is a process to go around this, you need a homebrew 3DS (Custom Firmware) and if you have any tool to extract the save file from your cartridge.
The process would have to go somewhat like this:
- Extract save file from both games (cartridge and VC game)
- Get both saves to your PC and use a save file editor (there are plenty online)
- Transfer your Pokemon from the cartridge save to the VC save file
- Overwrite your old VC save with your modified one.
That would be a way to do it, is a lengthy process, but worth it if you really want to do it.