Short answers, pulled from the story.
Venera 4 measured the Venusian atmosphere as 90 to 93 percent carbon dioxide, 7 percent nitrogen, 0.4 to 0.8 percent oxygen, and 0.1 to 1.6 percent water vapor. It also found the surface to be extremely hot and the atmosphere far denser than scientists had expected.
Venera 4 entered the Venusian atmosphere on the 18th of October 1967. The descent lasted 93 minutes before signal transmission terminated.
Venera 4 was the first spacecraft to survive entry into another planet's atmosphere. During entry, the heat shield temperature rose to 11,000 degrees Celsius and cabin deceleration reached 300 g.
The radar altimeter on Venera 4 had an integer ambiguity of 30 km, meaning the same signal could correspond to multiple altitudes. The team misread a return that was actually at about 55 km as being at 26 km, leading to the incorrect conclusion that the probe had landed.
Venera 4 detected a magnetic field at Venus that was 3,000 times weaker than Earth's. No radiation belts were found, and the hydrogen corona was 1,000 times less dense than Earth's.
The atmospheric composition data from Venera 4 was critical to the design of Venera 7, which made the first soft landing on Venus in 1970. The mission also showed that Venus probes decelerate almost instantly on atmospheric entry, a finding that shaped the design of Venera 5, 6, and subsequent spacecraft.