Vernacular, along with dialects, is the growing medium of the literary language. In addition, vernacular means, especially those that have a vivid expressiveness, are widely used in the speech of native speakers in the informal situations, when playing the corresponding social roles. In The Divine Comedy, Dante combined vernacular and solemn book vocabulary, pictorialism, and drama. The mature poet abandoned the rhythmic decorations and clauses, concluding that philosophical poetry is more clear and rigorous designs. In describing hell, exquisite, courteous speech is inferior to vernacular. Dante was not confused by the combination of high and low. After all, this is life. His devils, thieves, killers, robbers speak the language of the vernacular.
Several of these questions are opinion, so I can't really help with those, but I can answer the first one.
After World War I, the League of Nations was created to try to help keep the peace and solve problems between nations. The same went for the United Nations after World War II. There were also the treaties that ended the wars. (You'll have to decide whether or not these were actually successful.)
