Short answers, pulled from the story.
The Hobbit was first published on the 21st of September 1937 by George Allen and Unwin with a print run of 1,500 copies, which sold out by December of that year. The book went on to sell an estimated 35 to 100 million copies globally since its publication.
Tolkien recalled in a 1955 letter to W. H. Auden that he was marking School Certificate papers in the early 1930s when he found a blank page and was suddenly inspired to write the sentence "In a hole in the ground there lived a hobbit." He finished the manuscript by late 1932 and lent it to friends including C. S. Lewis before it reached a publisher.
A student of Tolkien's named Elaine Griffiths introduced the manuscript to Susan Dagnall, a staff member at George Allen and Unwin, when Dagnall visited Oxford in 1936. Dagnall showed the book to Stanley Unwin, who had his 10-year-old son Rayner review it. Rayner's favourable comments settled the decision to publish.
Tolkien drew heavily from the Poetic Edda and Prose Edda, from which he took most of the dwarf-names and the name Gandalf. The dragon Smaug and the cup-theft plot were shaped by Beowulf, which Tolkien counted among his "most valued sources." William Morris, George MacDonald, Jules Verne, and medieval texts about Jewish history also contributed to the story's characters and structure.
The most significant revision came when Tolkien was writing The Lord of the Rings and needed The Hobbit to fit his new conception of the One Ring. He rewrote the Gollum chapter, making Gollum aggressive and desperate rather than agreeable, and the revised text became the second edition published in 1951. A third edition in 1966 updated the text to renew the United States copyright after an unauthorized paperback appeared from Ace Books.
The first stage adaptation was performed in March 1953 by St. Margaret's School, Edinburgh. Gene Deitch produced a short animated film in 1966, Rankin and Bass made an animated television film in 1977, and Peter Jackson directed a three-part live-action film series between 2012 and 2014. BBC Radio 4 broadcast an eight-part radio drama in 1968, and Nicol Williamson recorded an abridged audio version on four long-playing records in 1974.