Short answers, pulled from the story.
Wolfgang Amadeus Mozart completed the score for Don Giovanni on the 28th of October 1787. This completion occurred just one night before its world premiere at the Estates Theatre in Prague.
The world premiere of Don Giovanni took place at the Estates Theatre in Prague on the 29th of October 1787. The venue had been known as the Comital Nostitz National Theatre when it opened four years earlier and was directed by the composer himself.
Luigi Bassi sang the title role of Don Giovanni as a baritone during the Prague premiere. Giuseppe Lolli portrayed the Commendatore while Teresa Saporiti played Donna Anna and Antonio Baglioni took the tenor part of Don Ottavio.
Mozart specifies three trombones that appear only during the final moments of act two in Don Giovanni. The score also calls for timpani, basso continuo consisting of harpsichord and violoncello, double woodwinds, two horns, and two trumpets.
The Vienna premiere of Don Giovanni took place on the 7th of May 1788 at the Estates Theatre. Mozart composed three new pieces specifically for this production to accommodate different singers including Francesco Morella and Caterina Cavalieri.