Short answers, pulled from the story.
Johann Sebastian Bach composed the Mass in B minor between 1748 and 1749. He assembled the Symbolum Nicenum and the remainder of the work during these final years before his death in July 1750.
Johann Sebastian Bach dedicated the Kyrie-Gloria Mass BWV 232 I to Augustus III to secure the title of Electoral Saxon Court Composer. He presented this copy along with a formal petition on the 27th of July 1733 after Augustus II died on the 1st of February 1733.
Only five of the twenty-seven movements in the Mass in B minor by Johann Sebastian Bach are written in B minor. Twelve movements including the final ones of each major section are written in D major which serves as the relative major key.
Karl Riedel led the first full public performance of the complete Mass in B minor in Leipzig in 1859. Carl Philipp Emanuel Bach had previously conducted a documented public performance of the Symbolum Nicenum section in Spring 1786 at a benefit event for the Medical Institute for the Poor in Hamburg.
Two autograph sources survive including parts for the Kyrie and Gloria deposited in Dresden in 1733 and a score compiled between 1748 and 1750. The personal handwritten manuscript held by the Berlin State Library entered UNESCO's Memory of the World International Register in 2015.