3dstool VS open_agb_firm

For open-source tools, Project CTR includes ctrtool to extract many 3DS formats including CIA, and makerom to build an NCCH, CIA, or CCI file. It's a bit old so I'm not positive it'll work exactly, but there's a guide on extracting a CIA using ctrtool and 3dstool, then rebuilding it using makerom and 3dstool.

You can rip the game to a cia file using GM9, and then on a PC use ctrtool and 3dstool to extract cia contents, extract the romfs from that, and then extract the romfs contents which will have all the game data files. I will warn you though that everything is in special Nintendo formats and it's different in some games. You may or may not be able to convert them to a normal PC audio format with various tools.

Link: https://github.com/profi200/open_agb_firm/releases/tag/alpha_2023-10-6

Don't forget about emulators! Especially if you have a "new" system - you can even play some (mostly 2D) PS1 games, and some N64 games on it, and everything older. On an "old" system you are more limited though - SNES games that use a SuperFX chip (such as SM RPG, Yoshi's Island, Star Fox, and some other ones) will run slow, but Genesis and 8-bit systems will run no problems. And you can run GBA games - on "new" you can even use the system's gyroscope for games like WarioWare Twisted or Yoshi Topsy-Turvy through mGBA, and on any system you can use injects or open_agb_firm - they both run games natively using the ARM7 CPU - the same one GBA uses, carried over into the DS, and it's still included in the 3DS.

Github

Use open_agb_firm. It's a firm, so it's activated in the same way as GodMode9, hold START while turning on the 3DS. You should be able to download it via Universal Updater. open_agb_firm uses the 3DS hardware to give you the same experience as playing on a real GBA.

That depends on how you are running the game on your 3DS. The best way is with open_agb_firm, in which case you will probably need to convert it with https://exelotl.github.io/gba-eeprom-save-fix/ (as linked from https://github.com/profi200/open_agb_firm ).

If you're playing a GBA game, open_agb_firm or a VC inject are your best bets.

You could use open_agb_firm to play your GBA games instead.

Because unfortunately mGBA is a little bit laggy on the 3DS. It’s terrific for game boy and game boy color games, but I digress. You could use something like open agb firm which runs games using the 3DS’ built in gba hardware natively without any lag or slowdowns.