General Motors Co's  strategy to make its luxury Cadillac marque its lead electric vehicle brand is the automaker's final opportunity to turn the unit around and make it a success, a top executive said on Monday.  "We don't have any chances left with taking Cadillac to a really new place," newly appointed GM President Mark Reuss told Reuters on the sidelines of the Detroit auto show.  In a move first reported by Reuters, GM said on Friday that a Cadillac would be the first vehicle built on the No. 1 U.S. automaker's "BEV3" platform to challenge electric carmaker  Tesla Inc .