Many...MANY! Instead of a re-start, I'd just buy another cartridge. I bought all the consoles I could find that were different and/or unique. I play every day and start a new town on the first day of each year. Sometimes I have to wipe an old town to continue this weirdness but, currently, there...
Game data is stored on the cartridge. Swapping the cartridges between 3DS consoles will allow you to play the games on whichever 3DS you want. Photos, however, are stored on the SD card, which can also be swapped.