What flag is the flag bearer carrying at the beginning of the Russian military parade?

Ula means long live in Russian

That flag refers to the flag that commemorates the Soviet armed forces’ contribution to the motherland in order to immortalize the achievements of the Soviet people in the Great Patriotic War from 1941 to 1945. To express gratitude to the ancestors who defeated the fascist invaders for their meritorious service, the Soviet Union will be awarded the honorary title to the 79th Infantry Army of the 1st Belorussian Front, 3rd Assault Army, and the 79th Infantry Army of the 1st Belorussian Front rising from the Reichstag Building in Berlin, Germany on May 1, 1945. The assault flag of the 150th Infantry Division of Idriz with the Order of Tuzov 2nd Class as the victory flag.

That is, a Soviet flag with slogans such as "Long Live the Great Soviet Motherland" written on it

It is a symbol of the victory of the Soviet Patriotic War and one of the national symbols of the Soviet Union. Every year the Red Square military parade is displayed in various ways.