Just download the right version of the "otherapp payload" for your firmware version
I have followed the 3ds guide and according to that i have downgraded my new 3ds xl from 11.2.0.35 to 10.4. But in settings menu of 3ds the firmware version is still 11.2.0.35 so should i download "otherapp payload" for 10.4 or for 11.2.0.35???