Dragon Ball: Advance Adventure

Cheat mode:
Press L, R, Up, Down, L, R, Left, Right, R(2), Right at the title screen to unlock a fourth mini-game, all bonus characters, and extras,

Boss mode:
Successfully complete the game with Goku and Krillin.

Extra mode:
Successfully complete story mode with Goku.

Survival in free battle mode:
Successfully complete story mode with Goku.

Rock breaking and Korin's Tower mini-games:
Successfully complete the game with Goku.

Small Fry Fight mini game:
Collect all the Dragonballs in extra mode to unlock the Small Fry Fight mini game. If you collected enemy portraits in extra mode, you will also be able to use those characters in the Small Fry Fight mini game.
Information in this section was contributed by JamilHingloti.

King Piccolo:
Successfully complete the game with Goku.

Krillin:
Successfully complete the game with with Goku

Piccolo:
Successfully complete the game with Krillin.

Cyborg Taopaipai in tournament mode:
Defeat Cyborg Taopaipai in the last level of tournament mode.

Juckie Chun in tournament mode:
Defeat Juckie Chun as Goku in story mode.

Piccolo in tournament mode:
Successfully complete the game as Krillin.

Son Gohan in tournament mode:
Defeat Son Gohan as Goku in story mode.

Taopaipai in tournament mode:
Defeat Taopaipai as Goku in story mode

Tenshinhan for tournament mode:
Defeat Tenshinhan as Goku in story mode.

Survival in one-on-one mode:
Defeat Grandpa Gohan in Krillin's Story mode.
Information in this section was contributed by Chris Hardewig.

Bonus free battle mode characters:
Defeat Juckie Chun, Taopaipai, Son Gohan, and Tenshinhan in the story mode free battles to unlock the corresponding character in free battle mode. Defeat Cyber Taopaipai in survival mode after unlocking Piccolo to unlock Cyber Taopaipai in free battle mode. Successfully complete the game with Gokou and Klylin to unlock Piccolo in free battle mode.

Sound test:
Successfully complete Boss Rush mode to unlock the sound test selection at the options menu.

Hint: Defeating Pilaf the second time:
When you face Pilaf the second time (in the level after The Red Ribbon Army Base level), just make sure he is on one side. Then, jump and hit him several times. Jump again and hit him several times. Keep doing that on the spot. He may hit you sometimes, but not enough to kill you. If the bombs explode on you, just get up and carry on until he dies. This is a guaranteed simple way to win.
Information in this section was contributed by Jamz.

Hint: Opening red doors:
In order to open the red doors you must successfully complete the story mode with Goku, which will unlock Extra mode. Once you play in Extra mode, all the red doors will be open.
Information in this section was contributed by Jamz.

Hint: Multiple attacks in normal battle:
Charge the Kamehameha and press L.
Information in this section was contributed by Keitarô Urashima.

Hint: Multiple attacks in one-on-one battle:
Charge The Kamehameha, jump and press L.
Information in this section was contributed by Keitarô Urashima.