Short answers, pulled from the story.
Vedic Sanskrit appeared between 1500 and 1200 BCE when a group of people moved from regions north of the Indus River into northwest South Asia. The Rigveda, containing 1,028 hymns composed during this period, stands as the earliest attested text in any Indo-Aryan language.
Pānini composed his Eight-Chapter Grammar around the 5th or 4th century BCE to create the most comprehensive ancient grammar ever recorded. His work became the foundation of Vyākaraņa and included four thousand grammatical rules organized through meta-rules and technical metalanguage.
Retroflex consonants absent in earliest Vedic developed gradually during oral transmission by generations of reciters likely originating through contact with Dravidian populations inhabiting central Gangetic plains. These sounds emerged as part of phonetic shifts influenced by constant interaction with Dravidian speakers over two millennia.
Sanskrit spread across South Asia, Southeast Asia, Central Asia, and parts of East Asia including China, Myanmar, Indonesia, Cambodia, Laos, Vietnam, Thailand, and Malaysia. Inscriptions dated between 300 and 1800 CE attest to this wide geographic distribution where it served as the language of religion, high culture, and political elites.
Sanskrit began declining after the 12th century coinciding with Islamic invasions creating Sultanates and later Mughal Empire. The fall of Kashmir around the 13th century ended premier centers of literary creativity perhaps due to fires engulfing capitals or Mongol invasion of 1320.
The Spitzer Manuscript discovered near Kizil Caves dates to about the 2nd century CE and represents the oldest known philosophical manuscript in Sanskrit. This artifact confirms the presence of Sanskrit literature in regions outside the Indian subcontinent during early centuries of the common era.