1. Yes, smacking your child on any part of their body, including the wrist, is violence. You're trying to make some kind of "a lot of violence might be wrong but just a little bit of violence can be useful" point? I don't get it.
2. No, I don't agree that "imprisoning children is wrong". Sometimes children commit horrible crimes, like murder, and they need to be imprisoned. If you want to say that grounding your child is also a form of imprisonment, it feels like a stretch, but sure, we can call that imprisonment too. I don't get what the point is, though.