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