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