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