A mod of BootNTR which will allows you to choose the version of NTR you want to load (and it is also much faster than regular BootNTR).
Install the .cia file through FBI and run it.
Copy the .3dsx file into sdmc:/3ds/BootNTRSelector/ and run it through the New Homebrew Menu.
How to use
Launch BootNTRSelector through your method of choice and follow the on-screen instructions, no extra steps or files are required.
BootNTRSelector will now default to whichever NTR version you selected last.
Notes for Old3DS users
You need to use one of the Mode3 releases in order to use NTR with extended memory games (such as Monster Hunter, Pokémon Sun/Moon, Smash Bros, etc.). Mode3 has no effect on New3DS.
Launching BootNTRSelector before the home menu is completely loaded may result in a crash / error. So before launching it, wait a couple of seconds for the home menu to be fully loaded.