Short answers, pulled from the story.
The R-7 Semyorka was a Soviet missile developed during the Cold War and the world's first intercontinental ballistic missile. It was successfully tested on the 21st of August 1957, flying 6,000 kilometers from Baikonur Cosmodrome to Kura Missile Test Range. It later became the basis for the most launched rocket family in history, with over 2,000 flights.
The R-7 was developed by OKB-1 under Sergei Korolev, with design work beginning in 1953 in Kaliningrad in Moscow Oblast. The propulsion system was developed by Valentin Glushko's bureau, OKB-456, which produced the RD-107 and RD-108 engines using a four-combustion-chamber configuration.
The R-7 required nearly 20 hours to prepare for launch and could remain on alert for no more than 24 hours due to its liquid oxygen fuel, which boils off quickly. Its massive launch complexes were visible to American U-2 spy planes and could not be hidden. These limitations reduced the planned deployment from 50 launch pads to just 6, and experts later called its ICBM role a "blunder" and a "monster."
The R-7's first successful long-range flight took place on the 21st of August 1957, covering 6,000 kilometers from Baikonur to Kamchatka. Earlier attempts on the 15th of May and the 11th of June 1957 both failed, due to a booster fire and an electrical short respectively.
A modified version of the R-7, designated 8K71PS, was used to launch Sputnik 1 into orbit on the 4th of October 1957, less than seven weeks after the missile's first successful test flight. The same basic rocket design that had been developed to carry a thermonuclear warhead was adapted into the world's first orbital launch vehicle.
R-7 derivatives have completed over 2,000 flights, making it the most launched rocket family ever. R-7-based rockets had recorded over 1,840 flights across more than 50 years of continuous service in various modifications, with the Soyuz family still in operational use.