Short answers, pulled from the story.
Mary Poppins premiered on the 27th of August 1964 at Grauman's Chinese Theatre in Los Angeles. It was released to universal critical acclaim and became the highest-grossing film of 1964 in the United States.
Mary Poppins received thirteen Academy Award nominations and won five: Best Actress for Julie Andrews, Best Film Editing, Best Original Music Score, Best Visual Effects, and Best Original Song for "Chim Chim Cher-ee". The thirteen nominations set a record for any film released by Walt Disney Studios.
P. L. Travers repeatedly refused to sell the film rights to Walt Disney from 1938 onward because she did not believe a film would do justice to her books. Disney finally obtained the rights in 1961 after more than twenty years of periodic persuasion, including a visit to Travers's home in Chelsea, London.
Yes, Mary Poppins was Julie Andrews's feature film acting debut. She had a successful stage career prior to the film, including originating the role of Eliza Doolittle on Broadway in My Fair Lady.
Made on an estimated budget of $4.4-6 million, Mary Poppins earned $44 million in worldwide theatrical rentals in its original run and was reported to be the most profitable film of 1965 with a net profit of $28.5 million. Walt Disney used those profits to purchase land in central Florida to build Walt Disney World.
The animated sequences used the sodium vapor process rather than the more common bluescreen method. Actors were filmed against a white screen lit with sodium vapor lights, and a prism-fitted camera filtered the light onto a separate reel to produce an unusually precise matte. The film won the Academy Award for Best Visual Effects in 1965 for this technique.