NO. NO PUEDES.
Sacado del hilo de emuNAND Tool de GBA:
What is NOT possible?
This tool does not enable you to magically use the Gateway (and clones) on a non 4.x system version.
You can't inject games.
You can't flash the Gateway mode to the 3DS.
You can't modify the firmware (no region bypass, backups,...).
You can't extract any keys.
You can't downgrade your 3DS with this tool. It only modifies the emuNAND on your SD card.
You can't use a NAND from another 3DS on your 3DS.