Hey there!

This guide will briefly explain how to unlock bonus levels. They can be found by going to "BONUS MISSION" from the main menu. There you will find 3 "hidden" levels. These levels are:

1. Hesperia Railways
2. Kundang, Indonesia
3. TV Station, Jakarta

These levels are the ones you run for the "Bonus Missions" category. However, to access them, you must unlock them first.

To do so, hold SELECT and mash left and right trigger. This should eventually unlock all of them by sheer brute force. However, should you need exact codes for reference:

1. SELECT (hold) - L + R (together) - L + R (together) - L + R (together) - L + R (together)
2. SELECT (hold) - L - L - R - R
3. SELECT (hold) - L - R - L - R

(Source: this article)

Hope this helps!

Have fun speedrunning!