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