Short answers, pulled from the story.
Napoleon Bonaparte crowned himself Emperor of the French on the 2nd of December 1804 at Notre-Dame de Paris. The Senate had proclaimed him emperor just two weeks earlier on the 18th of May 1804.
The phrase emphasized governance over people rather than ownership of land because old kings owned France as personal property. Napoleon claimed he ruled with consent from citizens while his office resembled the previous role of First Consul under the Republic.
His reign lasted exactly 111 days before final defeat at Waterloo which occurred on the 22nd of June 1815 ending his rule permanently. He was then exiled to Saint Helena where he died on the 5th of May 1821.
President Bonaparte officially became Napoleon III Emperor of the French from the 2nd of December 1852. That date mirrored his uncle's coronation anniversary exactly 48 years prior.
Napoleon III lost power after capture at the Battle of Sedan on the 4th of September 1870. His wife Eugenie de Montijo served as empress regent while he was overseas commanding armies and de facto rule transferred to her on the 28th of July 1870 before formal deposition.