This^doesn't ntr get's cleared out of RAM when you boot agb_firm?
Exactly what I also thought, thanks ^^This^
The agb_firm completely reboots the system (on both new and old 3DS's) and basically turns the system into a gba. This reboot would clear NTR out of RAM and as far as I know, it wouldn't be possible to make NTR survive this reboot.