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.
Find all the secret rooms in the mansion.
Complete the auto map by visiting every room in the mansion.
Watch a train arrive and leave at any station.
Get the kids blamed for shop lifting.
Read 15 teletext pages.
Save the Man in Black.
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.
Defeat the Fire boss.
Buy all possible shop items..
Defeat the Water boss.
Push all the rubber ducks into the water in the Laundry Room.
Defeat the Air boss.
Die 1000 times.
Find an alternate title screen skin.
Find a secret room in the mansion.
Defeat the Earth boss.
Catch 200 objects.
Run the BASIC program everybody knows and loves...
Score 100 baskets in total.
Reunite with Heather and the Old Lady.
Go on a most excellent adventure with the Professor.
Clean 100000 things.
Meet up with Alice and Sim.
Buy an item from a shop.
Earn £10000 from jobs, junk yards and other winnings.
Kidnap Mr Deck from the TV Studio.
Take your first train ride.
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.
Complete all other achievements.
Reach the end of the game having cleaned one million things.
Clean 1000000 things.
Find all the alternate title screen skins.
Get the high score on all the arcade games.