No. They state in no uncertain terms that ROMs are illegal and that both ROMs and emulators are damaging to the console industry. See the related links section for the official Nintendo legal information page.
An illegal copy of a game, usually copied onto the computer, but can also be hacked into game systems like the Wii.
You can't.
you cant the 3DS didnt has been hacked yet
Note that most ROM sites on the net distribute illegal versions of ROM files. It is illegal to download any commercial ROM. Opinions 80% to 90% of SNES and Gameboy ROMS are out of circulation, made...