Hacker Riku at GBATemp has managed to inject GBA roms to official GBA emulator on 3DS. This is the first time the official GBA emulator on 3DS can be used for something other than the 10 games Nintendo made available for Ambassador 3DS owners.
Nintendo offered Nintendo 3DS Ambassador Program as a way of showing appreciation for the people who bought their 3DS before the price drop. The program includes 20 virtual console games in total, 10 NES and 10 GBA games. Even though Nintendo made NES games available for public later, GBA games were never made available thus making ambassador consoles precious.
Official GBA emulator on 3DS is very accurate. It uses the hardware emulation for accuracy. That makes in-game home menu, sleep function and savestates impossible but it is a price to pay i guess.
Credits to Riku at GBATEMP
GBA rom injection is possible on all 3DS models. That means 3DS, 3DS XL/LL, 2DS, New 3DS and New 3DS XL/LL. You will need PBT CFW (for o3DS and 4.5 firmware only) or Pasta CFW (up to 9.2 both for o3DS and New 3DS). Gateway doesn’t support this yet, so i would advise using Pasta CFW instead. Also you can only use this on sysNAND, emuNAND doesn’t work for GBA titles.
The process involves installing stuff to sysNAND so i would advise to do a good reading before applying. Also having sysNAND backups can only help.