How do I patch the .xdelta3 file onto the .nds rom?
https://gbatemp.net/threads/patching-using-xdelta.320880/page-2
Use the option to patch ignoring checksum with xdelta3 if it doesn't patch normally, but check if it works in an emulator or something. (sometimes applying the patch more then once to get it to work, if you didn't do a complete dump of your game from your cartridge).