A. By definition, the RC is feature complete. The only changes made after the RC are bug fixes and performance tweaks. If you have the RC installed, it's performing well for you, and you're not experiencing problems, then installing all the post-RC builds isn't really worth the effort in most cases. Just wait for the release to manufacturing version and install that. If you don't have the RC build, it's certainly worth installing the RC of the OS.
This is different from new Windows builds in the beta stages. It's very common during the beta cycle for newer builds to have additional functionality, so installing new builds as they are released can be advantageous.
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