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