Nothing. You don't battle any other trainers or nothing.
If I am right, it should be by entering hall of fame
My time was 21:23:08.
some secret Pokemon aren't real like Freeza or Deserta thats just regirock and regice you can catch them by watching on youtube MunchingOranges' pokemon sapphire walkthrough but first you MUST POST HALL OF FAME :)
After beating the Pokémon League, your rival will escort you to the Hall of Fame.
You have to beat the Pokemon League.
pokecommunity
contest hall
beat elite four
You have to enter the Hall of Fame.
there is 1 in vendurof town:)
You must deliver the Ruby and Sapphire item to Celio at the One Island pokemon center in Leafgreen first. Become part of the Hall of Fame in Sapphire next. Now you can trade anytime, go upstairs in a pokemon center and talk to the lady who leads you to the Trade Center (middle lady for sapphire, right lady in leafgreen). Link up and you can start trading.
you beat the elite four