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