Article Learning Russian via Latin in the 17th Century suggests that in the 17th century Russian existed in a state of diglossia, where the vernacular Russian significantly differed from the written Slavonic - not unlike the situation in Europe of that period, where local spoken languages coexisted with written Latin (this state of affairs in Russia is also referred to in this question.)^1 This was apparently followed by a period where the literary language (at least for unofficial purposes) was French.
I am looking for a short timeline/recap of the evolution of Russian from its medieval diglossia to modern single spoken and literary language (either as an answer or as a reference.)
Wikipedia article History of the Russian Language gives limited information on the official status and proportion of Russian vs. Slavonic:
The official language in Russia remained a kind of Church Slavonic until the close of the 18th century, but, despite attempts at standardization, as by Meletius Smotrytsky c. 1620, its purity was by then strongly compromised by an incipient secular literature.
Regarding the development of literary language it says:
At the same time, there began explicit attempts to fashion a modern literary language as a compromise between Church Slavonic, the native vernacular, and the style of Western Europe. The writers Lomonosov, Derzhavin, and Karamzin made notable efforts in this respect, but, as per the received notion, the final synthesis belongs to Pushkin and his contemporaries in the first third of the 19th century.
^1 See also Wikipedia on Old Church Slavonic:
Church Slavonic maintained a prestigious status, particularly in Russia, for many centuries – among Slavs in the East it had a status analogous to that of Latin in Western Europe, but had the advantage of being substantially less divergent from the vernacular tongues of average parishioners.
and Wikipedia on Old East Slavic:
The political unification of the region into the state called Kievan Rus', from which modern Belarus, Russia and Ukraine trace their origins, occurred approximately a century before the adoption of Christianity in 988 and the establishment of the South Slavic Old Church Slavonic as the liturgical and literary language. Documentation of the Old East Slavic language of this period is scanty, making it difficult at best fully to determine the relationship between the literary language and its spoken dialects.