When you beat the game once you get an extremly hard diffuculty mode, like you have to fight Mobile suits that you fought in the end of the first game and Gundums are more often in the game (GOOD LUCK!!)
Federation Shield For Austin's Zaku 1
Successfully complete the game, then play
practice mission 1 with Austin's Zaku 1.
Successfully complete it and you should have a
heavy Fed shield like the Gundam's, and a few new
Successfully complete the game to unlock another
set of missions.
Play As Sayla
Get three "C" ranks or below on the Federation
missions to unlock Sayla.
Play As Garma Zabi
Get an "S" rank in Simulation Program 2 to unlock
Play As Char Aznable
Get an "S" rank in Simulation Program 1 to unlock