Short answers, pulled from the story.
McCartney was inspired by Pete Townshend of the Who, who described their September 1967 single 'I Can See for Miles' as the loudest, rawest, dirtiest song the band had ever recorded. When McCartney heard the record, he found it polished and restrained, so he wrote the genuinely raw song Townshend had only claimed to have made.
In British English, a helter skelter is a fairground attraction consisting of a tall spiral slide wound around a tower. McCartney used the image as a symbol of descent, describing it as a ride from the top to the bottom, evoking the fall of the Roman Empire.
The Beatles' first take of 'Helter Skelter,' recorded on the 18th of July 1968, lasted 27 minutes and 11 seconds. The final album version came from the 9th of September 1968, when the band recorded 18 takes of approximately five minutes each.
Charles Manson told his followers that 'Helter Skelter,' along with other White Album songs, contained a coded Beatles prophecy of an apocalyptic race war. At the scene of the LaBianca murders in August 1969, the phrase was found written in victims' blood on a refrigerator door, misspelled as 'HEALTER SKELTER.' Lead investigator Mike McGann and other law enforcement figures later disputed the claim that this interpretation was the actual motive for the murders.
Notable covers include Siouxsie and the Banshees, whose 1978 version appeared on their debut album The Scream; Motley Crue, who included it on Shout at the Devil in 1983; and U2, who recorded it live at the McNichols Sports Arena in Denver on the 8th of November 1987 and used it to open Rattle and Hum. Aerosmith recorded a cover in 1975, released on their 1991 compilation Pandora's Box, where it charted at number 21 on the Album Rock Tracks chart.
A live version of 'Helter Skelter' recorded during McCartney's Summer Live '09 tour and released on Good Evening New York City won Best Solo Rock Vocal Performance at the 53rd Grammy Awards in 2011. It was McCartney's first solo Grammy since he won for arranging 'Uncle Albert/Admiral Halsey' in 1972.