What is the name of James Bond's boss, known by a single letter?

Which actor played James Bond the most times in the official Eon series, with seven films? Which actor played James Bond in 'Casino Royale' (2006)? Which actor played James Bond in 'GoldenEye' (1995)? Which actor played James Bond only once, in 'On Her Majesty's Secret Service'? In which year was 'Star Wars' (later titled 'A New Hope') released? In which year was 'Jaws' released? In which year was 'Titanic' released? In which year was 'The Wizard of Oz' released?