Short answers, pulled from the story.
The North Caucasian languages are a proposed grouping of between 34 and 38 distinct languages spoken in the Caucasus region, predominantly in the north. The grouping consists of two well-established families: the Northwest Caucasian family and the Northeast Caucasian family. Whether these two families share a common ancestor remains a contested hypothesis among linguists.
Linguists Sergei Starostin and Sergei Nikolaev are the researchers most associated with the proposal. They argued that the two North Caucasian families descended from a common ancestor approximately five thousand years before the common era. Their 1994 classification provided the main internal structure for the hypothesis, though the methodology they used has been disputed.
Ubykh, a Northwest Caucasian language, has 84 consonants. Archi, from the Northeast Caucasian branch, is thought to have 76. Both figures represent exceptionally high levels of phonetic complexity and are central to the argument for grouping the two families together.
Tsez, a Northeast Caucasian language, has 126 locative suffixes. This figure arises from a series of locative cases intersecting with a series of suffixes that mark motion relative to a location. Depending on the analysis, these suffixes are sometimes described as noun cases.
No. The Kartvelian languages, which include Georgian, Zan, and Svan, were once labeled South Caucasian and considered alongside the North Caucasian families. They are now classified as an independent language family with no accepted genetic relationship to the North Caucasian languages.
The ASJP 4 automated computational analysis, conducted by Müller and colleagues in 2013, also grouped the North Caucasian languages together. However, the researchers explicitly declined to conclude whether the grouping reflected genetic inheritance or mutual lexical borrowing, because the result was generated automatically.