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 first dream world in nightmare mode.
Walk through portals 30 times.
Open a door in nightmare mode.
Watch the credits to the end.
Get Bob safely to the end of the last level.
Scare five chess pieces.
Help Bob through the first dream world.
Complete the first 3 levels to learn the basics of the game.
Complete the game 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.
Skip five cutscenes.
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.
Play the game at 13:37.
Complete level 8 by moving only one apple.
Complete level 8 in the second dream world by having Bob take a shortcut.