Short answers, pulled from the story.
Julius Nepos ruled as western Roman emperor from the 24th of June 474 to the 28th of August 475, when he was driven out of Italy by the general Orestes. He continued to hold the imperial title in Dalmatia with full recognition from the Eastern Roman Empire until his murder on the 9th of May 480, making him the last widely recognised holder of the western imperial title.
The eastern emperor Leo I appointed Nepos in December 473 to lead an army against Glycerius, who had been proclaimed emperor by the Burgundian general Gundobad. Nepos landed at Portus near Rome in the spring of 474, deposed Glycerius without a fight, and was proclaimed Augustus in Rome on the 24th of June 474.
Nepos's newly appointed magister militum Orestes revolted, using the grievances of foederati troops who had been refused land grants, and marched on Ravenna. Unable to stop Orestes's advance, Nepos fled across the Adriatic to Salona in Dalmatia on the 28th of August 475, having ruled in Italy for 14 months.
Nepos governed from Dalmatia and continued to be recognised as the legitimate western emperor by Constantinople. Odoacer minted coins in his name after deposing Romulus Augustulus in 476, but took no action to restore him. Nepos was murdered on the 9th of May 480 by his own retinue members, the comites Ovida and Viator, at his villa near Salona.
Romulus Augustulus was the last emperor to rule Italy, and his name coincidentally combined those of Rome's legendary founder Romulus and its first emperor Augustus. By the 6th century, historians including Marcellinus Comes, Procopius, and Jordanes all named Romulus Augustulus as the last western emperor, ignoring Nepos's continued reign in Dalmatia from 475 to 480.
Nepos was killed by two members of his retinue, Ovida and Viator, on the 9th of May 480. Ovida subsequently took control of Dalmatia. It was not until late 481 or 482 that Odoacer invaded Dalmatia, executed Ovida, and annexed the province, using Nepos's murder as his legal justification.