Short answers, pulled from the story.
Watching White Sun of the Desert before launch is a good luck ritual observed by all crew members boarding Russian space flights. The tradition has been in place for decades and applies to nearly every mission.
White Sun of the Desert drew 34.5 million viewers and was one of the most popular films of 1970. It went on to be regarded as one of the most popular movies of all time in the Soviet Union and attained the status of a classic.
The song was written by poet Bulat Okudzhava, with music by Isaac Schwartz. Okudzhava composed the lyrics at the personal request of director Vladimir Motyl, and the song was performed in the film by actor Pavel Luspekayev.
The film lost the 1970 USSR State Prize to By the Lake, which was considered ideologically correct by the Soviet authorities. White Sun of the Desert was seen as pure entertainment with low ideological value. It was not awarded official recognition until 1998, when President Boris Yeltsin granted it the Russian State Prize by special decree.
Andrei Tarkovsky and Andrei Konchalovsky were both offered the film before Motyl took over. Konchalovsky turned it down partly because he believed only American actors could carry a western-style lead role. Motyl himself initially declined but eventually agreed when no other directing work was available to him.
Pavel Luspekayev had both feet amputated in the 1960s due to injuries from World War II. He filmed the role of Vereschagin on prosthetic legs, taking regular rests because of pain, after refusing Motyl's offer to rewrite the character as a man on crutches. Luspekayev died in 1970, the year the film was released; it was his final role.