Short answers, pulled from the story.
Kevin Feige announced the Marvel Cinematic Universe Phase Three slate of films on the 28th of October 2014 at the El Capitan Theatre in Hollywood. This event revealed the full lineup including Captain America: Civil War, Doctor Strange, and the Avengers crossover films. The announcement was made all at once rather than being staggered to maintain suspense.
Sony Pictures and Marvel Studios officially announced their deal to share the character of Spider-Man on the 9th of February 2015. This agreement followed the 2014 Sony Pictures hack which leaked confidential data about the negotiations. Tom Holland was cast as Peter Parker in June 2015 under this partnership.
The Russo brothers directed Captain America: Civil War, Avengers: Infinity War, and Avengers: Endgame in Phase Three. They worked closely with other directors like James Gunn, Taika Waititi, and Ryan Coogler to ensure narrative consistency. Writers Christopher Markus and Stephen McFeely wrote the screenplay for the Russo films.
Black Panther was released on the 16th of February 2018 and was directed by Ryan Coogler. The film grossed over $1.3 billion worldwide and became a cultural phenomenon that transcended the superhero genre. It featured a cross-nation release in Africa and starred Chadwick Boseman as the title character.
Avengers: Infinity War was released on the 27th of April 2018 and Avengers: Endgame was released on the 26th of April 2019. These films were directed by the Russo brothers and written by Markus and McFeely. Endgame grossed over $2.7 billion and became the highest-grossing film of all time.
Spider-Man: Far From Home was released on the 2nd of July 2019 as the final film of Phase Three. The film was directed by Jon Watts and starred Tom Holland as Peter Parker. It grossed over $1.1 billion worldwide and served as the conclusion to The Infinity Saga.