The famous barrel roll in question was accomplished by Alvin M. "Tex" Johnston on August 7th, 1955 over Lake Washington, in the Boeign prototype which was the Boeing 367-80 which was similar in looks only, but completely different to the production model B707. The Boeing 367-80 was in other words a proof of concept aircraft wich was 132" in diameter whilst the 707 is 144" in diameter to accomodate 6 accross in economy.
You can do any manuever in any aircraft without causing any damage to the aircraft provided that you do not exceed any of the designed load limitations. Bob Hoover, a test pilot, is probably one of the most brilliant demonstration pilots in the history of aviation that has proven this fact in many aircraft.