Short answers, pulled from the story.
Philip V of Spain reigned for a total of 45 years, 9 months, and 8 days, surpassing Philip IV to become the longest-reigning monarch in the history of the Spanish crown. His total span results from two separate reigns: from the 1st of November 1700 to the 14th of January 1724, and again from the 6th of September 1724 until his death on the 9th of July 1746.
The war broke out because other European powers feared that a single Bourbon monarch ruling both Spain and France would upset the balance of power on the continent. Louis XIV's decision in December 1700 to issue letters patent preserving Philip's place in the French succession, despite his permanent move to Spain, heightened those fears and prompted England, the Dutch Republic, and Austria to form the Grand Alliance against France and Spain.
The Nueva Planta decrees, issued beginning in 1707, centralized Spanish governance under the Castilian administrative and political model, abolishing the separate charters of kingdoms that had previously enjoyed distinct legal status. The Crown of Aragon lost its autonomy as direct punishment for having supported the Austrian claimant during the War of the Spanish Succession, while Navarre and the Basque region kept their arrangements because they had backed Philip.
Philip V abdicated on the 14th of January 1724 due to his worsening mental health; he exhibited repeated episodes of mental instability throughout his reign and no longer wished to govern. He returned six days after his son Louis I died of smallpox on the 31st of August 1724, because his next heir, Ferdinand, was only ten years old and a lengthy regency was considered unacceptable.
Farinelli, a castrato singer, was appointed Musico de Camara of Their Majesties beginning in August 1737 and sang eight or nine arias for Philip and Elisabeth Farnese every night, accompanied by a trio of musicians. This nightly routine eased Philip's bouts of manic depression during the final decade of his reign.
Under the Treaty of Utrecht, Spain ceded Menorca and Gibraltar to Great Britain; the Spanish Netherlands, Naples, Milan, and Sardinia to the Austrian Habsburgs; and Sicily and parts of Milan to Savoy. Spain retained its New World empire and its possessions in East Asia, though its European presence was significantly reduced.