The Swedish king at this time was Adolf Fredrik, and his wife, the queen of Sweden, was Lovisa Ulrika of Prussia. Sweden has never had a king named Hugo, nor a queen Agnes, and Adolf Fredrik's father was not king of Sweden, as is implied. Otherwise, much of the historical details are correct - the Swedish uniforms are of a model that was introduced by Charles XII, and Sweden and Russia were often at war during the 18th century (albeit not during the short reign of czar Peter III).
Hopefully deliberate anachronisms: Chernobyl girl choir (with a pun "they glow" - of course the nuclear plant was non-existent until the 20th century) sings a song about the Red Army, which came in place after 1917.