Short answers, pulled from the story.
The Sahara spans North Africa and covers an area of 9,200,000 square kilometers, making it the largest hot desert in the world. It is the third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic. It stretches from the Red Sea and the Mediterranean to the Atlantic Ocean, bounded to the south by the Sahel.
The Sahara lies in the horse latitudes beneath the subtropical ridge, where high-pressure air sinks, warms, and dries, preventing clouds and rain from forming. The Atlas Mountains add a rain shadow that strips humidity from incoming weather. The desert records the highest rates of potential evaporation found anywhere on Earth.
The world's highest mean monthly maximum temperature, 47 degrees Celsius, was recorded in Bou Bernous, a remote town in the Algerian Desert at 378 meters above sea level. A sand temperature of 83.5 degrees Celsius has been recorded in Port Sudan. Daytime sand temperatures can easily reach 80 degrees or more.
Yes, the Sahara has alternated between desert and savanna grassland over several hundred thousand years in a cycle tied to changes in Earth's tilt. During wet phases known as the green Sahara, lakes such as Mega-Chad covered an estimated 350,000 square kilometers before 5000 BCE. The desert is expected to become green again in 15,000 years.
Ancient Saharan peoples included the Kiffian culture, who lived 10,000 to 8,000 years ago and stood over six feet tall, and the later Tenerian culture, both found at Gobero in Niger. The Garamantes built a desert empire around 500 BCE in Fezzan, Libya, tapping fossil water through mountain tunnels. A 5,600-year-old mummified boy was found at Uan Muhuggiag.
Most Saharan states achieved independence after World War II. Libya became independent in 1951; Morocco, Sudan, and Tunisia in 1956; Chad, Mali, Mauritania, and Niger in 1960; and Algeria in 1962. France had conquered the regency of Algiers from the Ottomans in 1830 and expanded its rule across the region through the 19th and early 20th centuries.