It all depends on which game Ты have... I remember that to get to level 31 in crash Bandicoot 3: Warped, Ты need to get caught by the секунда Pteridactyl in the group of them near the end of level four. I'm not certain of this, so Ты should check it just in case.
I've got two: -Crash Bandicoot:Warped, on one of the motorcycle levels there is a yellow sign with an alien face on it. Crash the bike into it and Ты will be transported to a secret level Ты can't access anywhere else -In Crash Bandicoot:The Wrath of Cortex, start a new Профиль and type your name to be 'Wombat'. When the cutscene finishes, Ты will have unlocked everything, even the secret platform in the middle. That's all I know.