Short answers, pulled from the story.
Napoleon ruled the Principality of Elba from April 1814 until the 26th of February 1815. The Treaty of Fontainebleau signed on the 11th of April 1814 transformed the Mediterranean island into his personal possession.
The Congress of Vienna transferred sovereignty of the island to the Grand Duchy of Tuscany following these events. The principality dissolved completely as Napoleon lost all claim to rule over the territory.
Napoleon brought 870 men from France to establish a small army on the island. The force included 566 soldiers from the elite Garde Impériale infantry and cavalry units plus a remaining battalion of 300 grenadiers under General Antoine Drouot's supervision.
The Villa Napoleonica served as Napoleon's summer residence in Portoferraio during his time on Elba. This building stood near the Palazzina dei Mulini located 3.5 kilometers northeast within the historic town center.
On the 26th of February 1815 Napoleon escaped from the island after ruling for nearly ten months to retake power. He landed in southern France to begin the War of the Seventh Coalition before his defeat at the Battle of Waterloo.