Misc: what does 'i.r.a' mean?

Questions

Who wrote the ballet Harlequin's Millions ?

Of what composition did Tchaikovsky say "a piece from the heart. I can't wait for to be played" ?

Who composed Rhapsody on a Theme by Paganini ?

Humoresque was published in 1890 and has remained a favorite. Who wrote it ?

What composition was used as the theme of the Lone Ranger TV series ?