Short answers, pulled from the story.
The Walt Disney Company agreed to pay Paramount Pictures at least 115 million dollars for the worldwide distribution rights to Iron Man 3 on the 18th of October 2010. This transaction dissolved corporate friction and established total control for Marvel Studios under Disney. The deal marked the birth of a unified cinematic universe where every film would carry the Marvel Studios logo without a distributor's branding.
Iron Man 3 focuses on Tony Stark saving himself from the psychological wreckage of the Battle of New York by confronting post-traumatic stress disorder. Director Shane Black and co-writer Drew Pearce crafted a narrative that forced the billionaire playboy to confront his anxiety and feel inferior to the Avengers. The film opened with the Mandarin destroying Stark's Malibu mansion and leaving him to piece together mysterious explosions while battling his own mind.
Thor: The Dark World was released in the United States on the 8th of November 2013. The film followed Thor as he reunited with astrophysicist Jane Foster while portals linked worlds allowing Malekith and his army of Dark Elves to return. Production began in September 2012 in Surrey, England, with additional filming in Iceland and London.
Captain America: The Winter Soldier revealed that S.H.I.E.L.D. had been infiltrated by Hydra. The film followed Steve Rogers as he worked with S.H.I.E.L.D. and teamed up with Natasha Romanoff and Sam Wilson to expose a conspiracy involving a mysterious assassin known only as the Winter Soldier. The Russo brothers directed the film which was released on the 4th of April 2014 in the United States.
The orb in Guardians of the Galaxy was revealed to contain one of the Infinity Stones. The film was released on the 1st of August 2014 in the United States and featured Chris Pratt as Peter Quill alongside Gamora, Rocket, Drax the Destroyer, and Groot. The mid-credits scene featured Josh Brolin as Thanos who was introduced in The Avengers mid-credits scene.
Avengers: Age of Ultron was released in the United States on the 1st of May 2015. The film achieved a worldwide gross of over 1.4 billion dollars. It was the culmination of Phase Two and the first film to bring together all six Avengers including Captain America, Iron Man, Thor, the Hulk, Black Widow, and Hawkeye.