Short answers, pulled from the story.
Gaius Caesar Augustus Germanicus was born on the 31st of August in AD 12 at Antium. He accompanied his father Germanicus and mother Agrippina the Elder on military campaigns across Germania when he was four or five years old.
Tiberius died on the 16th of March in AD 37, and Caligula was hailed as emperor by members of the Praetorian guard at Misenum on that same day. He entered Rome on the 28th or the 29th of March with the consensus of the senate, equestrians, and common citizens.
Caligula introduced unprecedented taxes on taverns, artisans, slaves, hiring of slaves, edibles sold in the city, litigation anywhere in the Empire, weddings, porters wages, and prostitutes. These cumulative taxes doubled overall across his brief reign while property left to Tiberius passed to him.
In late AD 39 or early AD 40, Caligula ordered concentration of military forces in upper Germany where possibilities included operations against Chatti tribes around Hesse or Suebi east of Upper Rhine. He used opportunities in Germany to seize wealth from rich allies suspected of treason.
Caligula was assassinated in early AD 41 resulting from a conspiracy by Praetorian Guard officers, senators, and courtiers. Their plan was thwarted when Praetorians spontaneously chose uncle Claudius as next emperor.