This is a guide for patching a game with Luma's built-in LayeredFS feature. This requires the latest Luma3DS and b9s. They can be installed using the guide if you have not already.
You can dump RomFS from any game using Godmode9. The RomFS can be used with some patchers or for exploring and modifying the game files yourself. A detailed tutorial on dumping RomFS from games can be found here.
- Power off your console
- Boot your console while holding (Select) to launch the Luma configuration menu
- Use the (A) button and the D-Pad to turn on the following:
- “Enable game patching”
- In some cases it may already be enabled. If so, proceed to the next step
- For a full list of features that this setting enables, see Luma3DS' wiki
- Press (Start) to save and reboot
Patches that work with LayeredFS come as folders (or .zip archives) with the modified romFS files in them.
- Unzip the patch archive, if applicable
- Place the patch's files into the
/luma/titles/<titleID>
folder on your SD card
- Game titleIDs are 16 characters long and start with
00040000
- You can find the titleID of your game from the 3dsdb title database
- If your patch already comes inside a folder with the titleID, put that folder into the
/luma/titles
folder and not into another folder
- Launch your game from the HOME menu and the patch should activate
- If the game acts normal, make sure that you have enabled game patching and that the patch folder is correcrly placed
- If you get an arm11 exception, make sure that none of the patch files are corrupt
No.
NDS games run in NDS mode. They cannot be patched with LayeredFS as they do not have TitleIDs like 3DS games and apps do.
Your best shot would probably be to buy a flashcart (not sure how well rapid testing would work with them, but they do have support for cheats). An alternative you could look into is TWiLightMenu++, but I am not sure how cheats work with it, either. I think just a PC emulator might work best if you're developing the mods on a PC.