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