Become a Pokémon Trainer and catch, battle and trade amazing creatures called Pokémon! In this Special Demo Version, you’ll experience exclusive scenarios you won’t find anywhere else! You can get a head start on your adventure in the Hoenn region where you’ll encounter Pokémon with new Mega Evolutions! You’ll even be able to transfer the Pokémon Glalie, who now Mega Evolves, into your full version of Pokémon Omega Ruby or Pokémon Alpha Sapphire! In addition, certain items that you get while playing the Special Demo Version can be transferred to the full game version upon purchase!
Whether this is your first time playing a Pokémon game, or you’re an experienced Pokémon Trainer, this Special Demo Version has something for you. Head to the Nintendo eShop on your Nintendo 3DS system to download the demo today!
Please note, this is the same Special Demo Version that was previously given out by download code. If you have already received the Special Demo Version by download code, you do not need to download this.
— Nintendo What’s New