Short answers, pulled from the story.
NFL on NBC first aired on the 22nd of October 1939, when NBC's New York City flagship station W2XBS televised a game between the Philadelphia Eagles and the Brooklyn Dodgers football team. This was the first televised professional football game.
The Heidi Game was a 1968 nationally televised game between the Oakland Raiders and New York Jets in which NBC cut away with 1:05 remaining to air the film Heidi. The Raiders then scored two touchdowns in eight seconds to win 43-32, a finish millions of viewers missed. The incident led the AFL and other sports leagues to demand that networks broadcast all games to their conclusion, a requirement that is now standard in NFL broadcast contracts.
Gayle Sierens became the first woman to do play-by-play for an NFL regular season game on network television when she called the 27th of December 1987 game between the Seattle Seahawks and Kansas City Chiefs on NBC. Her broadcast partner was Dave Rowe.
Super Bowl XX, broadcast by NBC on the 26th of January 1986, drew an audience of 127 million viewers according to ACNielsen figures. It replaced the final episode of MAS*H as the most-viewed television program in history at the time, earning a 48.3 rating and a 70 percent share in the United States.
CBS agreed to pay US$4 billion over eight years, or $500 million per season, to take the AFC broadcasting rights from NBC after the 1997 season. NBC reportedly bid up to $340 million but declined to go higher. NBC Sports president Dick Ebersol stated the network would not pursue any property likely to cost at least $150 million per year.
NFL on NBC returned on the 6th of August 2006, with NBC Sunday Night Football as its flagship program. The network had been absent from NFL broadcasting for more than eight years after Super Bowl XXXII on the 25th of January 1998.