There is a prolonged scene in which the antagonists sneak around the mansion, attempting to shoot the dog with tranquilizer darts. One of them holds a dart up for the others to see. Throughout the scene they shoot inanimate objects and each other and are shown pulling the darts out.
Use of tranquilizer guns. At the end of the film, a man pulls a gun to escape a court room. He fires accidentally when the dog jumps at him and the bullet grazes the dog's ear.
There is no possession in the traditional sense, but the main protagonist spends a significant portion of the movie "channeling" the dog, which is completely out of his control and causes him to more or less mirror the dog's behaviour and speak the dog's thoughts.
Technically yes, although there was no sexual intent and the incidents are played for laughs. While channeling the dog, the main protagonist lunges at a woman's ankles on all fours with his teeth. She later identifies this in court at him "making improper advances toward" her. In another scene, he bites and tears the seat of a woman's dress. She identifies this in court as an "attack".
Near the end, a gun goes off and it is assumed that the dog died, only for a moment, he is alright.