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