At age 25, Elizabeth II became Britain's 40th monarch and vowed to dedicate her life to service and duty on behalf of her country. She is the constitutional monarch of 16 sovereign states, head of the 53 member Commonwealth of Nations, Supreme Governor of the Church of England, and head of the armed forces. Most notably, however, on September 9, 2015, she became the longest reigning monarch in British history. She has consistently adapted in order...