Diddy Posts Apology Video for Cassie Beating

Play video content Diddy's uttering his first words about the videotaped beating of Cassie ... saying he "takes full responsibility for his actions," and claims he's already gone to rehab. He posted a video Sunday morning, looking directly into camera, he said, "It's so difficult to reflect on the darkest times in your life, but sometimes you gotta do that. I was f***ed up. I mean, I hit rock bottom." A 2016…