Short answers, pulled from the story.
The Citrus genus originated in the foothills of the Himalayas near Assam, western Yunnan, and northern Myanmar. A DNA study published in Nature in 2018 confirms this origin location in the southeast foothills of the Himalayas.
A common ancestor began to split into the Citrus genus and the Poncirus group about 15 million years ago. This speciation event followed during the Late Miocene period between 11.63 and 5.33 million years ago.
Many cultivated citrus species are natural or artificial hybrids of just three core ancestral species: citron, pomelo, and mandarin. Almost all commercially important fruits like oranges, lemons, and grapefruits are hybrids created within the last few thousand years.
Seeds recovered from the Hala Sultan Tekke site in Cyprus date back to around 1200 BCE. Pollen from Carthage dates to the 4th century BCE while carbonized seeds from Pompeii date to the 3rd or 2nd century BCE.
World production of all citrus fruits reached 124 million tonnes in 2016 according to UN Food and Agriculture Organization data. About half of this total production consisted of oranges alone.