Here is the full list of all 58 Horace achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Complete all other achievements.
Reach the end of the game having cleaned one million things.
Complete the game.
Save the Man in Black.
Clean 1000000 things.
Don't save the Man in Black.
Win The One Tournament.
Defeat the helicopter boss.
Travel to the secret moon base.
Defeat the Ether boss.
Complete the auto map by visiting every room in the mansion.
Find all the alternate title screen skins.
Find all the secret rooms in the mansion.
Defeat the Fire boss.
Push all the rubber ducks into the water in the Laundry Room.
Defeat the Air boss.
Find a secret room in the mansion.
Buy all possible shop items..
Find an alternate title screen skin.
Die 1000 times.
Defeat the Water boss.
Read 15 teletext pages.
Defeat the Earth boss.
Reunite with Heather and the Old Lady.
Go on a most excellent adventure with the Professor.
Clean 100000 things.
Run the BASIC program everybody knows and loves...
Meet up with Alice and Sim.
Earn £10000 from jobs, junk yards and other winnings.
Get the kids blamed for shop lifting.
Kidnap Mr Deck from the TV Studio.
Get the high score on all the arcade games.
Catch 200 objects.
Score 100 baskets in total.
Take your first train ride.
Watch a train arrive and leave at any station.
Buy an item from a shop.
Help to sort the post.
Earn £1000 from jobs, junk yards and other winnings.
Help to make bricks.
Play an arcade game.
Earn £100 from jobs, junk yards and other winnings.
Help to wash dishes.
Spring Logan from prison.
Learn to play the drums.
Empty 10 bins.
Defeat the Nanobot Boss.
Defeat the K-Bot 100 Boss.
Use the Atlas Gloves to tidy up the village hall.
Of dead Old Men?
Return the blind man's cat.
Clean 10000 things.
Rescue the family from the burning house.
Venture out of the mansion.
Climb walls with the Shoees for the first time.
Clean 1000 things.
Clean up your first thing.
Completed basic robot training.