Here is the full list of all 18 Knock-knock achievements.
Chose to lock The Lodger inside the cabin and remain hidden
Turned into a doppelganger
Remembered the story of the Lost Child
Found five diary pages
Entered ten haunters
Managed to hide succesfully ten times
Found a diary page
Saw a fragment of reality
Managed to hide succesfully
Entered a haunter
Chose to go into the woods
Saw all fragments of reality
Touched the weeping one
Turned the light on in every room
Saw three fragments of reality
Entered a breach
Turned the light on in a room before a breach opened
Managed to hide succesfully five times