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