1) Regular android provides google with unlimited access to everything -- for all intents and purposes, google has root access to the phone. GrapheneOS applies the same restrictions to google software as any other 3rd party software, which means that you can control what data it has access to using the standard permissions approach.
2) If you disable it, sure. If not, then how do you know when it is communicating with google?
3) Private space is a separate profile, just with some UI enhancements to allow it to be used simultaneously to the main profile.
4) Yes.
5) Probably. Why is this relevant?
6) There is no real option to transfer applications between, and definitely no option to add links to the home screen from private space.