Short answers, pulled from the story.
Classical Hollywood cinema is a narrative and visual style of filmmaking that first developed in the 1910s-1920s during the silent film era. It became the dominant style of American cinema from 1927, with the advent of sound film, and lasted until the 1960s.
The Big 5 studios of the classical Hollywood era were MGM, Warner Bros., 20th Century Fox, RKO, and Paramount. These studios operated a star system and kept directors, actors, and creative personnel under long-term contracts.
The 180-degree rule is a continuity editing guideline that creates an imaginary axis between the viewer and the action, allowing audiences to clearly orient themselves within the position and direction of actors across cuts. It was one of the foundational devices of classical Hollywood's visual style.
D. W. Griffith is credited with breaking the grip of the Edison Trust monopoly and helping cinema fulfill its artistic potential in the United States. His 1915 film The Birth of a Nation, starring Lillian Gish, introduced numerous innovative visual techniques and helped establish the narrative conventions that would define classical Hollywood.
1939 saw the release of an extraordinary number of celebrated films, including The Wizard of Oz, Gone with the Wind, Stagecoach, Mr. Smith Goes to Washington, and Ninotchka, among many others. Film historians identify it as the likely apogee of the studio system.
Classical Hollywood cinema gave way to New Hollywood in the 1960s-1980s, marked by films such as Bonnie and Clyde and The Graduate. New Hollywood directors built on classical conventions but pursued more personal and experimental approaches, aided by a broader cultural mistrust of authority.