Here is the full list of all 10 Spoiler Alert achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Find all 3 hidden main treasures.
Get gold star score in all 10 levels in the Mariachi World.
Watch the credits from finish to start.
Uncomplete the main game.
Get gold star score in all 90 main levels.
Unlock all 3 main worlds.
Do the leap of faith in World 3, level 12 - without middle landing on the support block.
Jump more than 150 times.
Get squished flat as a tortilla.
Cause more than 10 time paradoxes.