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