Yes,they will deliver it to your room, or to where ever you are eating the following night. Personally I have never had an issue where there has been any left over though.
Yes - they will automatically keep any wine not used. They put your number on it and you collect it on your way into the restaurant the next time you are there.
Every cruise I've been on with RCI, I had every intention of saving wine till the following night......problem was, the bottle was always empty!!