Here is the full list of all 55 HROT achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Check the simulator
Complete all three episodes
Complete episode 3
Give a gastroscopy
Find Tuzex vouchers
Find a postcard from the creators of Project Warlock 2
Free 4 Ratters
Locate the secret level
Pet two dogs
Waste three minutes watching the model railway
Get through a level without damage
Early Access sauna is a cold place
Shoot down a flying pigeon
Have a gastroscopy
Find 50 different secrets
Kill a monster by knocking it off somewhere high with the footkick
Surprise the newt in the cabin
I really like this random stuff
Kill 35 monster types
Complete episode 2
Clean all mess after the Degustation
Find all plates in the Granny's Valley and bring them to the Degustation
Anger the bees and run away
A lot of wine
Kill Headsman in air during jump
Start the mining train
Get past wave 15 in Endless Mode
Kill or damage 10 monsters with landmines
Get past wave 10 in Endless Mode
Hit the enemy with a kicked grenade
Survive wave 5 in Endless Mode
Burn 4 monsters with one bottle
Complete episode 1
Find all secrets in a level
Gottwald's body missing
Achieve a score of 200 points on a handheld game
Complete 6 different levels on Very High Difficulty
Discover a secret of Vyšehrad Castle
Kill 500 monsters in total
Run over 10 monsters
Gib a horse
Hit an enemy with the soccer ball
Kill all monsters in a level
Find a second pistol
Kill 5 monsters with a sickle in a row without damage