Here is the full list of all 20 Back to Bed achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Complete the game in nightmare mode.
Spend 10 minutes in one level.
Complete the first dream world in nightmare mode.
Open a door in nightmare mode.
Complete levels 1-30 in under 45 minutes.
Complete level 8 in the second dream world by having Bob take a shortcut.
Allow Bob to be woken by a dog, an alarm clock, a whale train and a manhole.
Send 10 wheel clocks over the edge.
Get Bob safely to the end of the last level.
Scare five chess pieces.
Skip five cutscenes.
Watch the credits to the end.
Play the game at 13:37.
Help Bob through the first dream world.
Walk through portals 30 times.
Make Bob walk over the edge 10 times in a single level.
Retry a single level 5 times.
Complete level 8 by moving only one apple.
Complete the first 3 levels to learn the basics of the game.
Use the fast forward function for a combined 5 minutes.