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