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