Short answers, pulled from the story.
The Saka language is an extinct Eastern Iranian language that was spoken in the Tarim Basin within what is now southern Xinjiang, China. It served as the primary tongue for two ancient Buddhist kingdoms known as Khotan and Tumshuq.
The Saka language existed from 100 BC to 1,100 AD with documents surviving from the fourth century through the eleventh century. The language became extinct after invading Turkic Muslims conquered the Kingdom of Khotan and the region became fully Turkified by the end of the eleventh century.
Contemporary documents identify the people of Khotan as Hvatanai while linking Khotanese and Tumshuqese to the Aqtala culture that developed since approximately 1000 BC. Some scholars suggest two Saka-speaking tribes settled around 200 BC before Chinese records began but no invasion is explicitly recorded in surviving historical accounts.
Over 2,300 texts survive among the Dunhuang manuscripts while only fifteen exist for Tumshuqese. Harold Walter Bailey deciphered these documents which now reside in institutions like the British Library.
Invading Turkic Muslims conquered the Kingdom of Khotan leading to a gradual linguistic shift toward Turkic until the region was fully Turkified by the end of the eleventh century. Mahmud al-Kashgari noted in the eleventh century that people still spoke their own language but knew little Turkic before the Islamicisation process ultimately replaced Saka with new patterns.