Short answers, pulled from the story.
Risk was invented by French film director Albert Lamorisse in 1957. It was originally released in France under the name La Conquête du Monde, meaning The Conquest of the World, before Parker Brothers acquired it and released it in the United States in 1959.
The Risk board contains 42 territories grouped into six continents. The most recent edition features a total of 83 attack routes connecting those territories, a number that has changed across different editions.
Australia is widely considered the easiest continent to defend because only two territories, Siam and Indonesia, connect it to the rest of the world. Fortifying either entry point can effectively seal the entire continent. It grants two bonus reinforcement armies per turn to the player who controls it.
Turtling is a defensive strategy where a vulnerable player fortifies so heavily that eliminating them costs more than opponents are willing to spend. The goal is to survive the early and middle game, then attack weakened opponents late and chain eliminations to win. The term comes from real-time strategy video games.
Risk was inducted into Games magazine's Hall of Fame in 1984, the Academy of Adventure Gaming Arts and Design Hall of Fame in 1995, and the National Toy Hall of Fame in 2021. Games magazine also included it in its Top 100 Games list in 1980, 1981, and 1982.
Risk: Legacy, released in 2011-12, is the edition that introduced the legacy game mechanic to board gaming. In a legacy game, permanent changes to the board and cards made during each completed session carry over to all future sessions, meaning no two copies of the game evolve in the same way.