Short answers, pulled from the story.
The Proto-Slavic language existed until around AD 500 before breaking apart into large dialectal zones by the 7th century. Archaeological and glottochronological evidence places the separation of the Balto-Slavic dialect ancestral to Proto-Slavic between 1500 BCE and 1000 BCE.
Diasporas have established isolated minorities of speakers across the globe, bringing the total number of speakers to an estimated 315 million at the turn of the twenty-first century. This makes them the largest ethno-linguistic group in Europe.
Scholars conventionally divide these languages into three subgroups: East, South, and West. The East group includes Russian, Belarusian, and Ukrainian while the West group comprises Polish, Czech, and Slovak and the South group contains Bulgarian, Macedonian, Serbo-Croatian, and Slovene.
All Slavic languages feature fusional morphology with fully developed inflection-based conjugation and declension except for Bulgarian and Macedonian. These two languages do not share this specific grammatical feature found in other members of the family.
Written documents from the 9th, 10th, and 11th centuries already display local linguistic features such as rhotacism found in Slovene dialects within the Freising manuscripts. These manuscripts represent the first Latin-script continuous text in a Slavic language.