Short answers, pulled from the story.
Julius Nepos served as Western Roman emperor from 474 to 480. He inherited military command from his uncle Marcellinus and was installed by Emperor Leo I of the East after Glycerius seized power.
Julius Nepos entered Rome on the 24th of June 474 and deposed Glycerius without bloodshed. His forces landed at Portus near Rome where they were promptly proclaimed Augustus with backing from Zeno, Leo's successor.
Julius Nepos fled across the Adriatic Sea to Salona in Dalmatia on the 31st of October 475. He maintained his claim to the Western Empire from Dalmatia while receiving recognition from Emperor Zeno until his death.
Orestes commanded troops including foederati who resented the emperor for refusing land grants and marched on Ravenna instead. On the 28th of August 475 Orestes entered Ravenna with his army while Nepos escaped back to Dalmatia.
Romulus Augustulus was deposed by Odoacer on the 4th of September 476 but Julius Nepos continued ruling from Dalmatia until 480. Eastern historians later considered Romulus Augustulus final western ruler despite Nepos holding the title longer.