Red Sox pitcher Matt Barnes (left) was in Faneuil Hall on Wednesday with Sox president Sam Kennedy and team mascot Wally the Green Monster to show off the “Red Sox Showcase Powered by T-Mobile,’’ a customized 15-foot panel truck that allows fans to test their baseball skills through interactive games and activities. The showcase includes a batting cage, a virtual reality experience, a pitch accuracy station, a Green Monster selfie station, and a steal second base challenge. The truck is scheduled to visit dozens of cities and towns during the season. Its next stop will be at the Hunnewell Elementary School field in Wellesley, on June 25 from 11 a.m. to 3 p.m.