Viacom is launching a live and interactive gameshow via Facebook Watch in the UK. The company's global division, Viacom International Media Networks, has partnered with the social media platform to launch MTV Stax. It launches today, Monday February 18 at 4pm GMT. It marks the latest interactive quiz on Facebook's content platform following the launch of Fremantle's Confetti. MTV Stax is a a free-to-play game broadcast live on Facebook Watch three times a week for ten…