Hold Back while highlighting your character at the selection screen to unlock their alternate version, as indicated below. Their portrait will change to confirm correct code entry. Note: To select BOTR Iori and Leona or Orochi and Goentiz, you must first defeat them in Arcade mode.

AOF King
AOF2 Yuri
EX Geese
EX King
EX Yuri
Goenitz (must be unlocked first)
KOF94 Joe
KOF94 Ryo
KOF94 Robert
KOF95 Kyo
Omega Rugal
Orochi (must be unlocked first)
Orochi Chris
Orochi Iori (must be unlocked first)
Orochi Leona (must be unlocked first)
Orochi Shermie
Orochi Yashiro
RBFF2 Andy
RBFF2 Billy
RBFF2 Blue Mary
RBFF2 Mai
RBFF2 Terry
RBFF2 Yamazaki