Two small questions

[Mandros]

If I'm going for the ultimate challenge, which dungeons can I just skip?

Which games did the music for the Goddess Temple, and Opera House come from?

[Vincent]

For the ultimate challenge you must not finish the temple of water and of earth.

For Goddess Temple, it's a music of a Zelda game on Cd-i (made by Phillips), and for Opera House, it is the music of the opera from Final Fantasy 6.