CANNES — The 65th Cannes Film Fest opened with a yin-yang pair of post-pic parties, an elegant dinner at Agora followed by a rave-style ear-splitter at the Carlton Beach.After the Palais preem of Focus Features’ “Moonrise Kingdom,” an elite group of 600, including the pic’s Wes Anderson, Bill Murray and Bruce Willis, walked to the nearby Agora with white walls and subdued, rosy lighting. Hand it to the French for old-fashioned class: The main course was the poetic-sounding jarret de veau de Limousin. In English, it’s just called veal knuckle. Either way, the chef got a standing ovation. A much bigger crowd knuckled their way into the beach bash, which followed another Cannes tradition: wrangling with city permits. Due to paperwork, there was a last-minute change in venues, Carlton Beach filling in for the fancier but more remote Chateau du Suquet. It was loud, dark and filled with hundreds of partygoers, who drank champagne from illuminated glasses.