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 the game.
Reach the end of the game having cleaned one million things.
Clean 1000000 things.
Find all the secret rooms in the mansion.
Complete the auto map by visiting every room in the mansion.
Run the BASIC program everybody knows and loves...
Read 15 teletext pages.
Save the Man in Black.
Win The One Tournament.
Defeat the helicopter boss.
Travel to the secret moon base.
Defeat the Ether boss.
Defeat the Fire boss.
Catch 200 objects.
Defeat the Water boss.
Defeat the Earth boss.
Get the high score on all the arcade games.
Find a secret room in the mansion.
Push all the rubber ducks into the water in the Laundry Room.
Buy all possible shop items..
Defeat the Air boss.
Find an alternate title screen skin.
Reunite with Heather and the Old Lady.
Die 1000 times.
Kidnap Mr Deck from the TV Studio.
Meet up with Alice and Sim.
Watch a train arrive and leave at any station.
Go on a most excellent adventure with the Professor.
Clean 100000 things.
Take your first train ride.
Buy an item from a shop.
Earn £10000 from jobs, junk yards and other winnings.
Help to sort the post.
Help to make bricks.
Play an arcade game.
Earn £1000 from jobs, junk yards and other winnings.
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.
Complete all other achievements.
Don't save the Man in Black.
Find all the alternate title screen skins.
Score 100 baskets in total.
Get the kids blamed for shop lifting.