Short answers, pulled from the story.
George Harrison, Ringo Starr, Paul McCartney, Linda McCartney, and Denny Laine all performed on the recording. Additional musicians included Al Kooper on electric piano, Herbie Flowers on bass, and Ray Cooper on tambourine.
Harrison originally wrote the song for Ringo Starr to record, but after Starr rejected it, Harrison rewrote the lyrics as a tribute to John Lennon following Lennon's murder in 1980. The song references two Lennon compositions, "All You Need Is Love" and "Imagine."
The single spent three weeks at number 2 on the US Billboard Hot 100, kept from the top spot by Kim Carnes's "Bette Davis Eyes." It also reached number 1 on Billboard's Adult Contemporary chart.
It was the first recording to feature Harrison, McCartney, and Starr together since the Beatles' "I Me Mine" in 1970. It remained their last joint recording until "Free as a Bird" in 1995.
The basic track was recorded at Harrison's Friar Park studio between the 19th and the 25th of November 1980. Paul McCartney, Linda McCartney, and Denny Laine later visited Friar Park to record backing vocals as an overdub.
The song was released as a single from Somewhere in England, Harrison's ninth studio album, in May 1981. It later appeared on the Harrison compilations Best of Dark Horse 1976-1989 and Let It Roll.