Short answers, pulled from the story.
Giuseppe Mazzini founded Young Italy in 1832. Its goals were the liberation of Italy from Austrian occupation, princely despotism, aristocratic privilege, and clerical authority, with the aim of establishing a united Italian republic based in Rome.
The "mutilated victory" was a phrase coined by Benito Mussolini to describe Italy's dissatisfaction with the territorial settlements after World War I, particularly the Allies' refusal to grant Italy Fiume despite Italy joining the war in 1915 in exchange for promises of substantial territorial gains. Historians regard the phrase as a political myth used by fascists to fuel Italian imperialism.
Italian nationalism arose as a political force in the 1830s under the leadership of Giuseppe Mazzini, although its intellectual roots have been traced to the Renaissance, including Petrarch's 1344 patriotic poem "Italia mia."
The Italian Nationalist Association (ANI) was founded in Florence in 1910 by Enrico Corradini. It emphasized martial heroism, total sacrifice of individualism to the nation, discipline and obedience, and the grandeur of ancient Rome, and its extremist appeals attracted widespread support among Italians.
D'Annunzio mobilized two thousand veterans and seized Fiume by force, an action that drew international condemnation but was supported by a majority of Italians. His government in Fiume was eventually forced from power, though Italy annexed Fiume a few years later.
After 1945, Italian irredentism disappeared along with the defeated Fascists and the monarchy of the House of Savoy. The Italian Republic formally abandoned all territorial claims in the Treaty of Paris in 1947 and the Treaty of Osimo in 1975. The neo-fascist Italian Social Movement (MSI) was the only party to maintain explicit Italian nationalism as its stated ideology, becoming the fourth largest party in Italy by the early 1960s.