There is no "play 5 days early". The game launched on 1st of September. But those who can't afford to shell out 100 Euros have to wait 5 more days. Microsoft did the same bullshit with Forza. I didn't like it back then, I won't like it now.
Why would you want to play a Bethesda game 5 days early? The best time is several months after release, when the community has had time to fix the bugs.
No, not sure how they handle it. I think the upgrade applies to either a purchased version or Game Pass version, but if you don't buy or sub, you wasted $35