Here is the full list of all 29 Dream achievements.
Collect all the Dream bible pages.
Finish Act Three's Nightmare.
Finish Act Three.
Visit all the side dreams.
Finish Act Two.
Finish Act Two's Nightmare.
Eat all the cupcakes.
Finish Act One's Nightmare.
Find the mess on floor one.
Finish Act One.
Finish all four mazes without getting caught.
Leave on all the lights before sleeping.
Finish the graveyard puzzle in ten moves or less.
Find the memories of an old experiment.
Find a past project.
Epic support needed...
Show off your festive side.
Play the first bar of 'Counting Sheep'.