If Russia (that is, lands in Eastern Europe populated by proto-Russians in the 9th century) was somehow totally isolated from the rest of the world from the 9th century on (say, ISoTed to a virgin Earth), we'd likely see many petty kingdoms and republics (like that of Novgorod) emerging all over Eurasia over millennia, with their peoples speaking fast diverging dialects of Old East Slavic, and then mutually unintelligible, but still fairly similar Slavic languages (after a few centuries).
They would likely still be Pagans even in Year 1,000 after the Event, and worship their gods in wooden temples with magnificent carved wood decorations, while their rulers would reside in similarly built and decorated wooden palaces. Some forms of writing (probably Runic in style) would survive and spread, albeit slowly, but there would be no mass literacy beyond larger cities even after a thousand years of independent development.
With abundant resources of a virgin Earth, there would be little use for fossil fuels, and thus steam engine would not be invented as early as OTL, if at all. Military technology would stagnate as well, with armour limited to nobles, and most warriors going into battle unprotected and using light spears and swords.