Short answers, pulled from the story.
Salyut 5 was originally designated as OPS-3 within a secret Soviet military program known as Almaz. This classification concealed its true reconnaissance purpose from Western intelligence for many years.
Salyut 5 lifted off from Site 81/23 at the Baikonur Cosmodrome on the 22nd of June 1976 aboard a three-stage Proton-K carrier rocket with serial number 290, 02. The launch occurred precisely at 18:04:00 UTC.
The Soyuz 21 mission ended prematurely on the 24th of August 1976 because nitric acid fumes from a fuel leak contaminated the station atmosphere. These toxic fumes negatively impacted both the psychological and physical condition of cosmonauts Boris Volynov and Vitali Zholobov.
A faulty sensor detected unexpected lateral motion during the approach which triggered the Igla automated docking system to fire maneuvering thrusters unnecessarily. This error expended too much fuel for the crew to reattempt docking under manual control before returning to Earth on the 16th of October 1976.
Cosmonauts Viktor Gorbatko and Yury Glazkov stayed aboard Salyut 5 from their launch on the 7th of February 1977 until they departed on the 25th of February 1977. The short duration resulted directly from the station running low on propellant required for its main engines and attitude control systems.