I suggest to try this:
require:
SysUpdater (Jullian version)
Teracopy (a neat program that do clean copy paste)
SD formatter (clean sd card formatting)
1.Copy file of sd card somewhere with on your pc with Teracopy (so backup)
2.Instal SD formater and have these setting
http://prntscr.com/9mk5cc
3.Install homebrew on the fresh formatted SD card and look if it FAT32 encryption
4.Install a theme from theme shop in your sd card (for home menu hax)
5.Go in browserHax and launch homebrew
6.Install menuhax in your 3ds
7.Put sd in pc
8.Delete boot.3dsx and put updates folder (of 9.2.0-20E) in your sd card folder
http://prntscr.com/9mkb1u (Idk why I didn't delete it it lol)
9.Take the julian SysUpdater.3dsx and rename it boot.3dsx
10.boot manuhax and it will be sysupdater! when it launch it will look that freeze, but don't touch anything
when it start, don't touch anything for 10-20 next minute unless you are sure that you are on main menu, because of menuhax, booting the 3ds will take a while to boot (will show a black screen for 2-5 minute and after home menu launch) but do not touch anything. It tested and work at 100% first try on O3ds (need to be confirmed, I do not have N3ds XD). I can even prove with photo 2 of the 3 successfully downgraded 3ds