Regarding the excellent answer of Jill on the music to which we sing “Twinkle, Twinkle” and the “Alphabet Song”, found here: Who wrote the melody to the alphabet song?
I finally dug up my box of piano music and looked up the Bach version. Variations on a French Song, seven variations on the song using various dance metrical forms, is listed as written by Wilhelm Friedemann Bach in my book The Joy of Bach, Yorktown Music Press (1968). Born in 1710, Willy was the eldest of J. S. Bach’s twenty children. He died in 1784. There is no date of composition given in the book. These would, of course, precede the famous, and better, Mozart variations.