Short answers, pulled from the story.
Buster Keaton got his nickname at around eighteen months old after falling down a long flight of stairs without injury. A friend of the family named George Pardey reportedly said, "Gee whiz, he's a regular buster!" Keaton retold the story throughout his life, though in some versions he was six months old and credited Harry Houdini with the nickname.
Keaton adopted his deadpan expression as a practical adjustment during his childhood vaudeville act. He noticed that when he laughed as his father threw him across the stage, the audience laughed less. He stopped smiling to keep the audience's laughter going, and the expression became his professional trademark.
The General, released in 1926, is regarded as Keaton's greatest achievement. Orson Welles called it "the greatest comedy ever made...and perhaps the greatest film ever made." The film received mixed reviews on release and was considered a commercial disappointment, which cost Keaton his total creative control over his projects.
Keaton signed with Metro-Goldwyn-Mayer in 1928 and lost his artistic independence. The studio controlled scripts, forced him to use stunt doubles, and required scenes to be filmed multiple times in different languages. He descended into alcoholism and was fired by MGM on the 2nd of February, 1933, ending his career as a leading man in feature films.
Keaton performed all of his major stunts himself. During the filming of Sherlock Jr., a water tower torrent broke his neck, an injury he did not discover until years later. In Steamboat Bill, Jr., a two-ton building facade fell over him with only a window opening leaving a few inches of clearance around his body.
Keaton received an Academy Honorary Award, which was presented at the 32nd Academy Awards held in April 1960. The American Film Institute later ranked him as the 21st-greatest male star of classic Hollywood cinema in 1999.