MEVO & the Grooveriders "Demo" - Level 15 Diamond Gruv
I put "demo" in quotes because this is actually the files from the full game, just that they're unlocking the demo achievements. Note that this game never goes on sale, but is a couple dollars cheaper on Amazon if I remember correctly. My completion time for the demo was 2.8 hours :D
Full explanation/tutorial:
You can normally only get 11/40 achievements in the demo. That is, unless, you own the full game!
I would recommend getting 100% in the full game first.
If you've dropped the $10 on the full version of MEVO & the Grooveriders, you can get all of the achievements in the demo as well. Here's how:
1. Move the contents of the full game's folder elsewhere.
2. Through Steam support, remove the game from your library (you can get it back, don't worry; here's a guide on how to do that: https://imgur.com/a/oCpXQ)
3. Install the demo.
4. Open up the demo's folder, and replace the contents of it with the files from the full game.
5. Delete (or backup) your full game save at C:\ProgramData\mevo
One unfortunate thing is that the achievements will not pop retroactively from your save in the full game if you've already got 100% in it. The triggers for the achievements are only when they initially pop. You will need to play through the game a second time. Luckily, though, it'll be a lot faster this time around!
6. Launch the demo from Steam. You should be prompted to make a new save and type in your name for MevoWorld or whatever it's called. If not, make sure you've deleted your save.
7. Play through the entire game, getting all 40 achievements once again.
8. Enjoy your 29 new shiny red achievements!