Short answers, pulled from the story.
Friedrich Schlichtegroll published an obituary for Wolfgang Amadeus Mozart in 1793 within a volume titled Nekrolog. The account focused almost exclusively on the period before the family moved to Vienna and relied heavily on information from Nannerl and Johann Andreas Schachtner.
Georg Nikolaus Nisen died in 1826 having completed only a small portion of the work himself while others finished the project using his notes in 1828. The couple moved to Salzburg where Mozart had lived for much of his life up to age twenty-five to pursue documenting the composer's life.
Otto Jahn published a major biography of Wolfgang Amadeus Mozart in 1856 that introduced new standards of scholarship. This document remains active today circulating in versions revised first by Hermann Abert and later by Cliff Eisen with an English version produced in 1965.
Michael Lorenz established the correct name of the person for whom the Ninth Piano Concerto was written which challenged previous assumptions about the dedicatee of the piece. He also revealed surprising information that Mozart lived in spacious suburban quarters during a time when conventional scholarship asserted he moved there due to poverty.
David J. Buch criticizes the older tradition of scholarship for allowing rumor and imagination to fill gaps in the biography following the composer's death. The deification of Mozart in the pantheon of German masters led to hagiography rather than factual analysis of motivations behind compositions.