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