Short answers, pulled from the story.
Salyut 3 was a Soviet military space station launched on the 25th of June 1974, officially designated OPS-2 or Almaz 2. It was publicly labelled a civilian station to disguise its true purpose as a military reconnaissance platform, and the Soviet Union withheld most information about its design and missions.
Salyut 3 was equipped with a self-defence gun attributed to designer Alexander Nudelman. Accounts vary on the exact model, with candidates including the Nudelman-Rikhter Vulkan gun and the Rikhter R-23. After the final crewed mission departed, the ground commanded the weapon to fire; some sources say it fired to depletion, others describe three test firings.
Only one of three planned crews successfully docked with Salyut 3. Commander Pavel Popovich and flight engineer Yury Artyukhin, launched on Soyuz 14, spent fifteen days aboard the station in July 1974. The Soyuz 15 crew came within 40 metres but failed to dock due to a malfunctioning Igla rendezvous system, and the third planned mission was cancelled.
Salyut 3 carried the Agat-1 Earth-observation telescope with a focal length of 6.375 metres and an optical resolution reported as better than three metres. Cosmonaut Pavel Popovich recalled the station had fourteen cameras in total, including a topographical camera, a star camera, and a Volga infrared camera with a resolution of 100 metres.
Flight engineer Lev Demin was 48 years old during the Soyuz 15 mission in August 1974, making him the oldest person to fly in space up to that point. His record was broken the following year when Deke Slayton flew as part of the Apollo-Soyuz Test Project.
The station's Earth-return capsule was ejected on the 23rd of September 1974, with NASA reporting its parachute opened at 8.4 kilometres altitude; other sources say the main parachute failed but the film inside was recovered. Salyut 3 itself was deorbited on the 24th of January 1975, re-entering over the Pacific Ocean.