Does anyone know if a seventh grader can try-out for バスケットボール, バスケット ボール even if i dont know how to play?????

Well sure, あなた COULD try out, but chances are あなた wouldn't make it. The guys you'd be up against probably would have been playing for years. Of course, あなた could always go out for intramural ball または something where you'd be guaranteed a spot.