Eating on the Moscow-Dushanbe train?

I'm taking this train to Kazakhstan soon and wonder: does this train have a restaurant car?

If not, where in the Russian cities of Gryazi and Volgograd can I buy food near the station (the train makes long stops there)?

Also, what does food cost, both on the train (if available) and in Gryazi/Volgograd? And if there's a restaurant on the train, what currencies, if any, does it accept besides Tajik somoni and Russian rubles?

I know RZD Trains have Restaurant cars, but this is a Tajik-operated train