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