Short answers, pulled from the story.
The Punic language began to separate from its Phoenician parent around the time that Carthage became the leading Phoenician city under Mago I. This divergence occurred gradually, and scholarly attempts to delineate the dialects lack precision and generally disagree on the classification.
Neo-Punic refers to the dialect of Punic spoken after the fall of Carthage and after the Roman conquest of the former Punic territories in 146 BC. Around the fourth century AD, Punic was still spoken in what is now northern parts of Tunisia and Algeria.
Mago wrote 28 volumes about animal husbandry during the period before 146 BC. The Roman Senate appreciated the works so much that after taking Carthage, they presented them to Berber princes who owned libraries there.
Punic has 22 consonants and details of their pronunciation can be reconstructed from Punic and Neo-Punic texts written in Latin or Greek characters. In Late Punic and in Late Phoenician, certain letters underwent fricativization to other sounds in the 3rd century BCE.
Augustine of Hippo died on the 430th year and is generally considered the last major ancient writer to have some knowledge of Punic. He is considered the primary source on the survival of late Punic because he stated that Punic was still spoken in his region, Northern Africa, in the 5th century.