Most necessary:
Surf
Ice Beam
Plus 2 of the following:
Earthquake
Body Slam
Rock Slide
If you pick 2 of either of those 3 physical moves, EV train Walrein's Atk more than its Sp.Atk, since Surf and Ice Beam already earn STAB and you'd probably want a balance of Walrein's offenses.
Or, you can combine Surf and Ice Beam with Rest and Snore. If you choose this, Walrain should be holding a Chesto or Lum Berrry. Don't worry about losing that Berry (even if a foe Kecleon uses Trick on your Walrein), since items are completely restored after every Battle Frontier battle. Also, with Rest and Snore, don't EV train Walrein's Attack at all; focus more on Sp.Atk and Speed, since Walrein already has decent defenses.
No, Pokemon Sapphire Version does not have a Battle Frontier. However, Pokemon Emerald and Pokemon Platinum do have the Battle Frontier.
no
Sudowoodo
Pokemon Ruby and Pokemon Sapphire do not have the Battle Frontier, instead they only have the Battle Tower. It was not until Emerald version that the Battle Frontier was added to the game.
Its not at Battle Frontier, its at Pacifidlog Town
The battle frontier after the Pokemon League.
anything except the legendaries
Smeargle and Sudowudoo
the first island in emerald is battle frontier
No, the Battle Frontier can only be found in Emerald, Platinum and HeartGold/SoulSilver.
the battle frontier was called.....actually, i believe it was called the battle frontier.
No, because there is a battle fronteir in Emerald only.