Bomberman Hero
Hidden Planet Gossick
To get access the hidden planet, get 5 Gold Bomber Hero Medals and all of the Other-Dimension Bombs.

Slider Race
To get the Slider Race Option, get 3 Gold Bomber Hero Medals.
 Hidden Planet
 Gossick
 Slider Race
 Gold Bomberman
 Millian's Treasure
 Hunt
 Level Select
Gold Bomberman
To get the Gold Bomber option, complete the hidden planet.

Millian's Treasure Hunt
To get the Millian's Treasure Hunt option, get 6 Gold Bomber Hero Medals.
Credit For Codes Goes To: MetroidMoo via N64cc

Level Select
Press A, B, and Z. You will now have Level Select as an option.