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