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