Short answers, pulled from the story.
Giuseppe Piazzi, a Catholic priest at the academy of Palermo in Sicily, spotted Ceres on the 1st of January 1801. He observed this new body twenty-four times before illness forced him to stop his work on the 11th of February 1801.
The International Astronomical Union adopted a requirement on the 24th of August 2006 that a planet must have cleared its orbit, which Ceres failed to do since it shares its space with thousands of other asteroids. Bodies meeting the first definition but not the second became classified as dwarf planets, making Ceres the only dwarf planet inside Neptune's orbit.
Measurements from the Dawn spacecraft found Ceres has a mean diameter of about 940 kilometers and a mass suggesting a quarter of its total weight is water ice. Gravity data indicate Ceres is partially differentiated into a muddy ice-rock mantle or core surrounded by a less dense crust containing at most thirty percent ice by volume.
Ceres formed approximately 4.56 billion years ago as a surviving protoplanet between Jupiter and Saturn before being deflected into the asteroid belt during Jupiter's outward migration. Discovery of ammonium salts in Occator Crater supports this outer solar system origin since ammonia is far more abundant there than inside the belt.
NASA launched the Dawn spacecraft on the 27th of September 2007 as part of its Discovery Program, making it the first mission to visit either Vesta or Ceres. The mission ended on the 1st of November 2018 after the spacecraft ran out of hydrazine fuel used to maintain its orbit.