MIAMI — Lil Meech, an actor and rapper who gained fame under the tutelage of Hip Hop megastar 50 Cent, was arrested last weekend for his part in a convoluted scheme to steal hundreds of thousands of dollars worth of watches, police said. Police say that Lil Meech, whose real name is Demetrius Flenory Jr., didn’t honor an agreed-upon $200,000 payment for one expensive watch — then used the guise of a GQ photo shoot to persuade a downtown Miami jeweler to lend him a $275,000 Richard Mille Roberto Mancini edition watch on consignment, before trading it to another jeweler. Then, police said, when …