The Pink Flamingo Kid - S3-E17
Other mistake: When Eddie busts Cory filming him and his cronies, he spends a few moments intimidating Cory before snatching the camera out of his hands and throwing it against the ground. After Shawn breaks up the situation and notes that they broke the camera, Cory remarks that they didn't get the tape and proceeds to pull a tape from under his jacket. Cory's hands are both visible gripping the camera the entire time that Eddie is confronting him, and he didn't have the opportunity to retrieve the tape when Shawn intervened, so he couldn't have had the tape tucked away.
Answer: Topanga's middle name is never specified. Considering her sister's name is Nebula Stop-the-war Lawrence, Topanga's is probably something equally unusual.