The video shows "Back to Back" danced on the Saint-Petersburg Lermontov Ball (October 2014). The dance is danced 4 times, once for each couple. For bars 29-32 a variant is danced: instead of dancing out the ends and casting R to 2pl, 1c here dances out the sides, casts R and crosses in to 2pl.  1c then steps/dances down to 4pl.