Sorry for the late reply. I've been more busy with new work and so when I check this thread again, it's already filled with several new pages of posts so it's hard to keep track of everything.
I believe that you can downgrade emunand now with sysupdater. Another way would be replacing manually each system file with the 9.0 firmware files so that it becomes the same as your N3DS. However I'm not 100% sure on this part so I think it's best if you ask
@Ronhero since he's the one who came up with this method.
As for using FreeMultiPatcher in your N3DS, you can install it normally (it's a CIA app) and then you just need to run it so that the firmware becomes spoofed. You can get more details on FreeMultiPatcher's thread here in the forum if you want.