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