Short answers, pulled from the story.
Republic Pictures initially planned to release the film in December 1947 but withdrew it from the Venice Film Festival before its U.S. theatrical release. The studio ordered a truncated version with re-recorded dialogue which was officially released in 1950.
Orson Welles guaranteed delivery of the completed negative for $700,000 and agreed to personally pay any costs exceeding that amount. He shot the entire film in 23 days plus one day for retakes to meet this strict financial limit.
Jeanette Nolan played the role of Lady Macbeth after Vivien Leigh declined the part due to her husband Laurence Olivier's opposition. Other actresses including Tallulah Bankhead, Anne Baxter, Mercedes McCambridge, and Agnes Moorehead were approached but remained unavailable for the project.
Welles added sequences involving witches who create a clay figurine of Macbeth to symbolize his rise and ruin through voodoo-like magic. He also introduced a new character called the Holy Man to represent the struggle between Druidical pagan religion and Christianity while censoring double entendres from the Porter's speech.
Critics complained about Welles having his cast speak with Scottish burrs and modify the original text which led to overwhelmingly negative reactions. Republic Pictures subsequently ordered him to cut two reels and re-record the soundtrack so actors spoke in their natural voices instead of approximating Scottish accents.