Short answers, pulled from the story.
Pope Sixtus IV ordered the demolition of a ruinous chapel called the Cappella Maggiore in 1473. A new building rose on the same site under the supervision of Giovannino de Dolci between 1473 and 1481.
On the 15th of August 1483, Sixtus IV celebrated the first mass inside the completed space. That ceremony consecrated the chapel and dedicated it to the Virgin Mary.
The work concluded between 1508 and late 1512 under papal patronage. Pope Julius II commissioned Michelangelo to repaint the vault in 1508 despite the artist's reluctance.
Michelangelo painted The Last Judgment on the altar wall between 1535 and 1541 for Pope Paul III Farnese. This massive fresco replaced earlier scenes including the Nativity of Jesus and the Finding of Moses.
Restoration work on the ceiling began on the 7th of November 1984 and reopened to the public on the 8th of April 1994. Chemists decided to strip away all shadowy layers including animal glue, lamp black, wax, and overpainted areas as contamination.