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.
Watch the credits from finish to start.
Uncomplete the main game.
Find all 3 hidden main treasures.
Unlock all 3 main worlds.
Jump more than 150 times.
Get squished flat as a tortilla.
Cause more than 10 time paradoxes.
Get gold star score in all 90 main levels.
Do the leap of faith in World 3, level 12 - without middle landing on the support block.
Get gold star score in all 10 levels in the Mariachi World.