Short answers, pulled from the story.
Alexander I was Emperor of Russia from 1801 until his death in 1825, as well as the first King of Congress Poland from 1815 and Grand Duke of Finland from 1809. He was the eldest son of Paul I and Sophie Dorothea of Württemberg, and he ruled Russia through the Napoleonic Wars.
Alexander I refused to negotiate with Napoleon after Moscow was occupied and burned, delegating military command to generals including Mikhail Kutuzov. The French Grande Armee lost approximately 380,000 men dead and 100,000 captured during the campaign, which ended on the 14th of December 1812 when the last French troops left Russian soil.
Alexander I abolished the old Collegia and created new ministries, a Committee of Ministers, a State Council, and reorganised the Governing Senate as the Supreme Court. He founded three new universities at Saint Petersburg, Kharkiv, and Kazan, and created the legal category of 'free agriculturalist' in 1803 to allow voluntary emancipation of serfs. Plans for a constitution and parliament were drawn up but never enacted.
The Treaty of Tilsit was signed on the 25th of June 1807 after the Russian defeat at the Battle of Friedland. It created a Franco-Russian alliance under which Alexander joined Napoleon's Continental System, received a free hand over Finland, and was offered visions of joint influence over the Ottoman Empire and Asia. The alliance collapsed by 1810 partly because the Continental System devastated Russian trade with Britain.
Alexander I died of typhus on the 19th of November 1825 in Taganrog while traveling south due to his wife's illness. A persistent legend holds that he faked his death and lived as a Siberian hermit named Feodor Kuzmich; Svetlana Semyonova of the Russian Graphological Society concluded that Alexander's and Kuzmich's handwriting were identical, though the claim was never definitively confirmed.
Alexander and Napoleon shifted between opposition, alliance, and hostility. Alexander joined coalitions against Napoleon in 1805 and again after 1812, but between 1807 and 1810 the two were formally allied under the Treaty of Tilsit. Napoleon called Alexander a 'shifty Byzantine' and the Talma of the North. The alliance broke down over Poland, trade, and Napoleon's failure to support Russia against the Ottomans.