How do you unlock TT on diddy kong racing 64?

In the first level, race in Ancient Lake. On the right side of the road in the beginning of the race, there is a brown ramp. Drive on that ramp and you'll drive straight into the key. Unlocks: Fire Mountain

In the second level, go to Snowball Valley. Don't drive, because it's right at the beginning. Don't go straight, go left and keep going. Then turn and go straight and in a small cave there is a key. Unlocks: Icicle Pyramid

In the third level, start Crescent Island. Drive straight into the water and keep going. Watch left (don't drive left, though) For a small hole in a beam/pole. In the hole is the key. Unlocks: Darkwater Beach

When I find out Dragon Forests' Secret, I'll add it.