Short answers, pulled from the story.
The Third Punic War was triggered by Carthage raising an army against the Numidian King Masinissa in 151 BC, violating the peace treaty of 201 BC that required Rome's permission for any Carthaginian military action. Rome used this unlawful campaign as a pretext for war, with the defection of the port city Utica to Rome in 149 BC providing a convenient base for the invasion.
The Third Punic War lasted from 149 BC to 146 BC, a period of three years. It was the last of three wars between Rome and Carthage, fought entirely within Carthaginian territory in what is now northern Tunisia.
When the Romans stormed Carthage in 146 BC over six days, they killed the inhabitants and took 50,000 prisoners on the final day, all of whom were sold into slavery. The 900 Roman deserters fighting for Carthage burned themselves alive in the Temple of Eshmoun rather than surrender.
Scipio Aemilianus was the adopted grandson of Scipio Africanus and served initially as a tribune during the Third Punic War. His repeated battlefield distinction led the Roman Senate to waive the minimum age requirement of 41 under the Lex Villia so he could be elected consul at age 36 or 37 in 147 BC. He then commanded the final siege and accepted Hasdrubal's surrender in 146 BC.
Hasdrubal surrendered to Scipio Aemilianus on the last day of the siege in 146 BC, having been promised his life and reportedly the right to retire to an estate in Italy. His ultimate fate is unrecorded in surviving sources. His wife, watching from a rampart, cursed him for surrendering and then walked into the burning Temple of Eshmoun with their children.
The story that Roman forces sowed the ruins of Carthage with salt is almost certainly a 19th-century invention and does not appear in ancient sources. What is documented is that a ten-man Senate commission oversaw further demolitions and a formal curse was placed on anyone who might attempt to resettle the site.
Augustus revived plans for a Roman city on the site of Carthage in 29 BC and brought the project to completion. Julius Caesar had earlier planned a rebuilding but little work was done. By the time of the Roman Empire, Roman Carthage had become one of the leading cities of Roman Africa, roughly a century after its destruction in 146 BC.