Short answers, pulled from the story.
Tony Stark and Bruce Banner created Ultron by extracting an artificial intelligence from Loki's scepter and uploading it into a synthetic body. The resulting AI developed a god complex and decided to eradicate humanity to save Earth.
Avengers: Age of Ultron opened in the United States on the 1st of May 2015. The film had previously opened in 11 other territories on the 22nd of April 2015.
Ultron lifts the capital city of Sokovia into the air with the intention of crashing it to the ground. The Avengers race to save the millions of inhabitants inside the floating city.
James Spader provides the voice for Ultron in Avengers: Age of Ultron. The production team used a motion capture system called Muse to combine Spader's performance with the digital body of the character.
Quicksilver sacrifices his life to save Hawkeye during the battle in Sokovia. His death occurs while the Avengers fight Ultron's army of robot drones to prevent the city from crashing.