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