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