The sequel to "X-Men: First Class" is "X-Men: Days of Future Past," released in 2014. The film combines the original X-Men cast with the newer cast from "First Class," featuring a time-travel plot where Wolverine is sent back to the 1970s to prevent a catastrophic event that could lead to the extinction of mutants. Directed by Bryan Singer, it explores themes of prejudice and the consequences of actions across timelines.

"X-Men: First Class" serves as an origin story for the X-Men franchise, exploring the early relationship between Charles Xavier (Professor X) and Erik Lensherr (Magneto). Set during the Cold War, it highlights their differing ideologies regarding mutant rights and human coexistence. The film illustrates the formation of the X-Men team to combat the threat posed by Sebastian Shaw and his Hellfire Club. Ultimately, it addresses themes of acceptance, prejudice, and the moral complexities of power, setting the stage for the ongoing conflict between mutants and humans.

In "X-Men: First Class," Hugh Jackman made a brief cameo as Wolverine. For this appearance, he reportedly received around $100,000. His cameo was a nod to the character's popularity, although his role in the film was minor compared to his previous performances in the X-Men franchise.

Yes, "X-Men: First Class" is set in a different timeline within the X-Men film series. It serves as a prequel to the original X-Men trilogy, exploring the origins of key characters like Charles Xavier and Erik Lensherr (Magneto) during the early 1960s. The events of this film create an alternate timeline that diverges from the original trilogy, which is further explored in subsequent films like "X-Men: Days of Future Past." This restructuring allows for new character dynamics and plot developments while maintaining ties to the established universe.