Short answers, pulled from the story.
Louis XVI was the last king of France before the fall of the monarchy during the French Revolution. He reigned from the 10th of May 1774 until the abolition of the monarchy on the 21st of September 1792, and his execution by guillotine on the 21st of January 1793 ended more than a thousand years of continuous French monarchy.
Louis XVI was tried by the National Convention, found guilty of high treason, and condemned to death by a majority of one vote among 721 deputies. The key evidence against him included the discovery of the armoire de fer, a hidden safe in his bedroom containing compromising correspondence with foreign powers, and the Flight to Varennes, which confirmed suspicions that he was conspiring with Austria against France.
Louis XVI actively supported the American colonists from 1776, first by secretly sending supplies, ammunition, and guns, then by signing a formal Treaty of Alliance early in 1778 and going to war with Britain. French forces were instrumental in the Siege of Yorktown in October 1781, and the war ended with the Treaty of Paris of 1783, though it cost France 1,066 million livres financed entirely through loans.
On the 21st of June 1791, Louis XVI attempted to flee secretly with his family to the royalist fortress town of Montmédy near the Austrian border. He was recognized from his profile on a 50 livres assignat by Jean-Baptiste Drouet and arrested at Varennes-en-Argonne within 24 hours. The failed flight destroyed his remaining legitimacy and drove mainstream French opinion toward republicanism.
Louis XVI signed the Edict of Versailles, also known as the Edict of Tolerance, on the 7th of November 1787. It granted non-Roman Catholics, including Huguenots, Lutherans, and Jews, civil and legal status and the right to practice their faiths in France, effectively ending an edict that had stood for 102 years.
Both of Louis XVI's sons died in childhood before the Bourbon Restoration. His daughter Marie-Thérèse-Charlotte was released to her Austrian relatives in exchange for French prisoners of war and eventually died childless in 1851. She later lobbied in Rome for her father's canonization as a saint, but a memorandum in 1820 declared it impossible to prove he had been executed for religious rather than political reasons.