1st: Dictates whether a driver can choose a different tire before the stage from the drop-down box. Once the tire choice has been made, you keep that until the choice is allowed again, usually the first stage of a leg or after a Service Park. So, if you think that it is going to rain, you could use an intermediate or wet tire.
2nd: The France Cup is a little unusual in that you can drive more than 1 car in a rally. Think of it as you bringing 3 cars to a rally, then running the rally up to 3 times, once each in a different car. I only use one currently, but thinking about a second to do some sort of recon for my Group N car

You can drive any of your 3 cars as I understand it, but haven't put this to test.