Here is the full list of all 20 Project Nightmares Case 36: Henrietta Kedward achievements.
Finish the game without dying
Provokes Henrietta to hit the wall 30 times
Find the 4 lost masks in the house
Smash 50 cockroaches
Light the candle 20 times
Read all Henrietta's diaries
Find all the mansion keys.
Solve the picture puzzle in less than 5 minutes.
Solve the piano puzzle with less than 5 mistakes
Take less than 3 minutes to open the iron door.
Dodge the monster without getting eaten.
Hide 10 times in the library
Avoid being caught behind bars more than once by Henrietta.
Find all Shuel's cards.
Avoid getting your head cut off by a tool from the basement.
Burn 6 heads with light
Find the newspaper with Henrietta's story.
Find the mysterious stoves
Save Henrietta
Kill Henrietta