Bill Haley is shown performing at the start of part 2 as a solo act. In the 1950s (and indeed throughout his rock and roll career) he always worked in conjunction with The Comets. The band shown backing Haley at the start of part 2 is not The Comets.
The princess phone wasn't introduced until 1959, although this movie is set in 1956-57. Other telephones in the movie are also years ahead of their time.