Hebrew stopped being commonly used in 400 CE, and was then preserved as a liturgical language for Jews across the globe. It then, however, went through a complete revival with the rise of Zionism in the 19th and 20th centuries. The early speakers of Modern Hebrew mostly spoke Yiddish as their mother tongue, but Modern Hebrew has been strongly influenced by Yiddish.
When it comes to linguistic mysteries, the Basque language is the epitome. Some Basque people who reside in France and Spain speak it, but it is not related at all to a Romance language, which French and Spanish in fact are. It is also not related to any other language, with no theories that have managed to trace back to it’s roots. The only thing that’s been made clear is that is was around before the romance languages.
Farsi is a popular language spoken in modern Iran, Afghanistan, and Tajikistan. It’s actually the same as Persian, just under a different name. It is the direct descendant of Old Persian, which was the official language of the Persian Empire. Modern Persian came about in 800 CE, and today it has slightly changed.
Tamil is the official language of Singapore, Sri Lanka and Tamil Nadu. It is the only classical language that has made it’s way to the modern world, and is spoken by approximately 78 million people. Tamil continues to develop and is the 20th most commonly used language.