Short answers, pulled from the story.
"Tomorrow Never Knows" was released on the 5th of August 1966 as the final track on the Beatles' album Revolver, issued by EMI's Parlophone label. It was, however, the first song recorded during the Revolver sessions, with work beginning on the 6th of April 1966.
Lennon drew the lyrics from The Psychedelic Experience: A Manual Based on the Tibetan Book of the Dead, a 1964 book by Timothy Leary, Richard Alpert and Ralph Metzner. He found the book at the newly opened Indica bookshop, went home, took LSD, and followed its instructions, adapting lines such as "Whenever in doubt, turn off your mind, relax, float downstream" into the song.
The title came from a malapropism by Ringo Starr. In a television interview in early 1964, Starr uttered the phrase "Tomorrow never knows" while laughing off an incident at the British Embassy in Washington, DC, where a guest had cut off a portion of his hair. Lennon adopted the phrase to lighten the song's heavy philosophical lyrics.
All four Beatles created tape loops by disabling the erase head of a tape recorder and running a continuous loop of tape through the machine, causing it to overdub itself repeatedly. They supplied George Martin with around 30 loops; he selected 16 for the recording. During the overdubbing session on the 7th of April 1966, each loop ran on a separate BTR3 tape machine, held in tension by an EMI technician using a pencil, while the Beatles operated the mixing console faders.
"Tomorrow Never Knows" marked the first use of reversed sounds in a pop recording, including a backwards lead guitar part recorded by George Harrison and reverse cymbals. The Beatles' 1966 B-side "Rain" used the same technique but was issued more than two months before Revolver reached stores.
The producers of the Mad Men episode "Lady Lazarus", which aired in 2012, paid around $250,000 to use "Tomorrow Never Knows", described as about five times the typical cost of licensing a song for television. The Wall Street Journal reported that Lionsgate claimed this use marked the first time a Beatles master recording had been licensed for a television show.