Short answers, pulled from the story.
Ludwig Ritter von Köchel published his first comprehensive listing of Wolfgang Amadeus Mozart's works in 1862. The volume bore the title Chronological-thematic Catalogue of the Complete Musical Works of W. A. Mozart and contained 551 pages.
Neal Zaslaw released the ninth edition of the Köchel catalogue in 2024 with newly discovered pieces receiving numbers extending past 626 up to 721. This version abandoned strict chronological ordering for the main body while returning all previously numbered works to their oldest number.
The Köchel system divides Wolfgang Amadeus Mozart's output into five appendices labeled Anh. I through V where Appendix I contains lost authentic works and section V lists misattributed works. Section II holds fragments by Mozart himself, section III lists transcriptions made by others, and section IV covers doubtful compositions.
Leopold Mozart compiled partial lists of his son's early works before 1784. Wolfgang began a personal catalogue in February 1784 with entry K. 449 which allowed relatively precise dating of later pieces.
Works labeled spurious often carry attributions to composers like Johann Ernst Eberlin or Quirino Gasparini. Some pieces once thought to be by Wolfgang Amadeus Mozart were later identified as by Michael Haydn or Leopold Mozart.