Ok, here's everything you need to know to get this achievement.
In Total, there are 36 Side Missions. With few exceptions, side missions are triggered by the collection of CPs (Communication Points.) in the level. You simply touch them and they are active, offering a new side mission on the mission select screen.
There are 26 CPs total. If you have a mission available with an inactive CP, then it will show a Green border on the mission select screen rather than a red one.
Here's a list of the available Bonus Missions:
For the Racing levels, some tips ----
First, Some levels (Cooter Creek, Jade Plateau, and Skerries) have a shortcut that you are intended to find and use or you will never win.
Secondly, almost any vehicle can go lightning fast off road as long as you don't accelerate offroad. Just let yourself coast, you'll barely slow down at all.
Third, Before every race, there are four tones played and the light turns green, if you press the accelerator for the first time exactly on the fourth tone when the light changes, you'll get a boost.
Last thing, if you need to wreck a building for a race, (or in the regular game) this is key!! If your vehicle hits the building while airborne or tilted on its wheels, the parts of the building that you hit will automatically wreck. Some levels are built around this concept. If you see a rock touching a wall of a building, you're meant to drive over it to wreck the building.