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