Here’s an ad from the August 1 1931 edition of the Toronto Daily Star for a combined vaudeville and motion picture show.
I found a number of articles on Betty and Beth Dodge: the Intriguing People website, Classic Actresses, and Jazz Age Club all have pages on them. Betty Dodge was born in 1909 and Beth Dodge in 1910; they looked enough alike that they billed themselves as twins. When they were still teenagers, they toured Britain and then headlined the Folies Bergère show in Paris. They returned to North America in 1929. In 1931, they declared bankruptcy. Beth Dodge twice married and twice divorced Clarence Stroud, who was himself a twin. What happened to them after their career wound down is not known.
I couldn’t find anything on O’Brien and Hewitt, except that they appeared in Indianapolis in 1927.
Gold Dust Gertie was originally filmed as a musical. When musicals fell out of fashion, the film was released in the United States with all of its musical numbers removed, leaving it with a running time of 65 minutes. It was released in Europe with the musical numbers intact, but no known copy of this version of the film exists.