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
Get past wave 15 in Endless Mode
Get past wave 10 in Endless Mode
Survive wave 5 in Endless Mode
Find Tuzex vouchers
Waste three minutes watching the model railway
Find a postcard from the creators of Project Warlock 2
Gottwald's body missing
Surprise the newt in the cabin
Kill 5 monsters with a sickle in a row without damage
Discover a secret of Vyšehrad Castle
Run over 10 monsters
Burn 4 monsters with one bottle
Kill a monster by knocking it off somewhere high with the footkick
Kill Headsman in air during jump
A lot of wine
Check the simulator
Complete all three episodes
Complete episode 3
Give a gastroscopy
Hit an enemy with the soccer ball
Hit the enemy with a kicked grenade
Get through a level without damage
Shoot down a flying pigeon
Free 4 Ratters
Find all secrets in a level
Locate the secret level
Pet two dogs
Early Access sauna is a cold place
Have a gastroscopy
Find 50 different secrets
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
Start the mining train
Kill 500 monsters in total
Complete episode 1
Kill or damage 10 monsters with landmines
Gib a horse
Kill all monsters in a level
Find a second pistol