When Legasov was interrogated by KGB agent, he was looking at floor. In the next shot his head was tilted upwards.
The testimony Legasov gave in court was a critical part of the narrative, explaining how an RBMK reactor core can explode. In reality, Legasov didn't testify at the trial of Dyatlov, Fomin and Bryukhanov.
Moscow in March isn't green. It's still winter time.
Near the end of his analysis of the accident (at 51:10), Legasov states "The reactor core has now become a nuclear bomb." While written for dramatic effect, it is strictly speaking not the case. At best, it was a nuclear fizzle, or even just a criticality accident. While the basic mechanism of the initial energy release was indeed the same as in an atom bomb (a runaway nuclear chain reaction), a reactor core is unable to keep the critical mass assembled long enough to achieve the number of chain reaction generations necessary for a nuclear fission yield worth mentioning. Instead, the core blew itself apart, long before that happened. The yield of the initial nuclear transient that blew the lid off the core is estimated at under a ton of TNT equivalent, and the stronger steam/hydrogen explosion that followed, at about 10 tons. So it was not even in the kilotons range, which is considered little in terms of nuclear bombs. Even a 0.1 kt explosive yield - 100 tons of TNT equivalent - would have annihilated the complete building, and possibly the whole four-reactor complex.
Following the trial in Chernobyl in July 1987, an overhead camera shot pans over a stretch of the town. Though more than a year had passed since the town had been evacuated, the grass is still neatly kept and there are no branches strewn anywhere from rain and snowstorms.
Plastic windows did not exist back in 1986 in USSR. Road markings are also clearly of twenty-first century style.
The early scene stating that is in Moscow is actually in Kiev, Ukraine, looking down at one of the main historic areas on Khreshchatyk street.
Shcherbina mentions "Nazis", however the term "Nazi / Nazism" was not used in the Soviet Union. Soviets deliberately used the (incorrect) term "Fascist / Fascism" instead for Hitler and the Third Reich because "Nazi" is the shortened form of "National Socialist" and it might give negative connotations to the term "Socialism".