Misc: Which word is the Latin for 'pebble' and is now, applied to a branch of mathematics?

Questions

who advised us to 'break on through to the other side'?

who appeared on american bandstand in november of 1957 singing 'hey schoolgirl'?

Who are the two brothers in the band ac/dc?

Who asked the musical question "didn't i blow your mind this time"?

who asked the musical question "dont it make your brown eyes blue"?