Before, the demo was only accessible through club memberships and game purchases and never saw a public release.
The demo for Omega Ruby and Alpha Sapphire contains exclusive scenarios and new mega evolutions to take advantage of. Those who purchase a full version of either game will also be able to import the mega-evolving Pokemon Glalie and certain items over from the demo.
Nintendo notes that this is the same demo released earlier this year, and that there is no reason to download it if the previous code has already been used.
Omega Ruby and Alpha Sapphire are remakes of the Game Boy Advance Pokemon games from 2002 with several additions and differences.
Via IGN
Via IGN