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