I mean, everyone relies on everyone in a world economy, you need to come up with examples. You mean nuclear deterrence? The French are going to share their nuclear deterrence with the rest of the EU.
Yes, indeed. Although on paper UK also joins this venture, they depend on USA for their nuclear arsenal (subs).
On the long-term, EU might need more nuclear weapons for adequate deterrence, and also FR might not be so stable given alt-right over there. So any integration needs to be stable on paper.