The answer to question 2) is Basilio, Act 1, scene 7, Nozze di Figaro, which I finally got after trawling through all the librettos!
The photo is of Bryn Terfel, (rt), and Jose van Dam, (lft), as Don Giovanni and Leporello. They first sang this at Paris Opera in 1999, according to Terfel websites.
captainandy, I followed your suggestion, and found, not the oboe quartet, but the Act III quartet "I will wander alone ..." ("Andro ramingo e solo") from Idomeneo moved Mozart to tears when he sang it himself, according to his sister. So I get the champagne!