Street Fighter Zero 2

Fight against Mid-Level Bosses
To fight Mid-Level bosses use must not lose a single round and win five rounds with a super or custom combo finish. After the fifth win the new challenger will appear along with a short dialogue.
 
Use Chun-Li's Original Outfit
On the player select screen move to Chun-Li and then press and hold START. After five seconds press for the following outfits. 
  Blue  = Any P button
  Pink  = Any K button
  Green = All Three P buttons
  Grey  = All Three K buttons
Play as Evil Ryu (USA version only)
On the player select screen go to Ryu and press START. Now move R, U, D, L. Press and Hold START. While holding press any P or K button to enable Evil Ryu.
 
Play as Classic Zangief (USA version only)
On the player select screen go to Zangief and press START. Now move D, Lx4, Ux2, Rx4, D and you will land on Zangief again. Now press and hold start and then then press any P or K button.
 
Play as Classic Dhalsim (USA version only)
On the player select screen go to Dhalsim and press START. Now move L, D, R, U and you will land on Dhalsim again. Now press and hold start and then then press any P or K button.
 
Secret Stages
Note: The following codes must be entered by a player entering a game as a new challenger or they will not work.
 
To fight in a Grassy Area press and hold START. Move cursor to Sagat and keep it on him for five seconds. Now go to the character you want and release START, then press any button.
 
To fight at the Waterfall press and hold START. Move cursor to M.Bison and keep it on him for five seconds. Now go to the character you want and release START, then press any button.