Short answers, pulled from the story.
Paul McCartney wrote the song Let It Be after dreaming of his mother Mary Patricia McCartney in 1956. The dream told him to let it be and that all would be alright, which became the seed for the composition.
George Martin produced the single version of Let It Be and released it on the 6th of March 1970. This mix featured softer guitar solos and orchestral sections mixed low compared to the album version.
McCartney performed Let It Be during the Live Aid charity concert on the 13th of July 1985 facing a global television audience exceeding one billion people. His microphone failed for the first two minutes making hearing impossible for stadium attendees until David Bowie Bob Geldof Alison Moyet and Pete Townshend returned to stage to back him up.
Phil Spector remixed the track for the Let It Be album on the 26th of March 1970. His version included Harrison's second guitar solo overdub more prominent orchestration delay effects to Starr's hi-hat during the second verse and significantly increased backing vocal volume.
Take 27-A served as the basis for all officially released versions of the song. Take 27-B appeared in the film Let It Be alongside Two of Us and The Long and Winding Road.