The game was confirmed to be for the DS and DSi. But, since the 3DS has backwards compatibility, you can play it on there too.

Also, more on Zoroark's Illusion ability. The pokemon it "transforms" into is the second pokemon in your party. It changes into the shape of that pokemon and it's name is changed as well. It still retains it's Dark type but IDK if it uses the moves of the copied pokemon.