George Vernadsky was among many historians to speculate that Volodislav was Igor's eldest son and heir who died at some point during Olga's regency. Source: Internet
The text reads: "Prince Igor, opera in 4 acts with a prologue, words and music by A.P. Borodin, subject adapted from The Lay of Igor's Host." Source: Internet
The bass progression in the middle I found noted down on a scrap of paper, and the combination of the two themes (Igor's aria and a phrase from the trio) was also discovered among the composer's papers. Source: Internet