Short answers, pulled from the story.
Czech is spoken by over 12 million people including second-language speakers. About 10 million of those are residents of the Czech Republic, where a 2012 Eurobarometer survey found that 98 percent of citizens listed Czech as their first language, the third-highest proportion in the European Union.
The letter ř represents the raised alveolar non-sonorant trill, a sound described as somewhere between Czech r and ž. It is known to occur as a phoneme in only a few other languages, appearing in some dialects of Kashubian and formerly in Polish, but Czech is the only language where it exists as a standard phoneme across all speakers. It appears in the composer's name Dvořák.
The Czech National Revival was a cultural and linguistic movement that began in the mid-18th century and continued into the 19th century. Czech historians and philologists worked to restore Czech to prominence after the language had been suppressed following the Habsburg defeat of the Bohemian Revolt in 1620 and the dominance of German in subsequent centuries. Key figures included Josef Dobrovský, who published a grammar of Old Czech in 1809, and Josef Jungmann, who used that grammar to advocate for a Czech linguistic revival.
The Kralice Bible, published between 1579 and 1593, was the first complete Czech translation of the Bible from the original source languages. It became a foundational model for standard written Czech in the centuries that followed, and Josef Jungmann drew directly on its vocabulary when compiling his Czech-German dictionary between 1834 and 1839.
Czech and Slovak share a higher degree of mutual intelligibility than any other pair of West Slavic languages. A 2015 study with participants whose mean age was around 23 confirmed that high mutual intelligibility remained even after the 1993 dissolution of Czechoslovakia. The two languages share a common syntax, and their lexical differences stem largely from differing orthographies and minor morphological inconsistencies.
Common Czech, known as obecná čeština, is the vernacular spoken across most of Bohemia including Prague. It features simpler inflection patterns, vowel mergers such as /ɛː/ shifting to /iː/, and a prothetic v- added to words beginning with o-. Unlike Standard Czech, it is not codified and most Czechs associate it with informal or incorrect speech rather than a recognized variety.