I finished it. Like in many books: expect the unexpected, and you'll emerge victorious!
This game is awesome! It makes you swear like hell sometimes, and is hellish difficult. The name Unfair Platformer is completely correct!
For those who have problem with lvl 20, you make a giant amount of duplicates trying to cross the cliff so you can jump across them if you use them well.
The first thing I did was get enough points to buy the best wheels, best hull and the flamethrower. Result: Death now has a suitable vehicle to drive in