Angels have the Phone Box
If you upgraded from a qualifying OS (which you say you did), and you are not receiving Insider builds, then you should be good to go. Yes, you should be able to clean install as often as you need/like. If you do the slmgr /dlv and /xpr that should tell you what you need to know. I will mention this: I am on a system which used TPs from the start on a clean disk - no upgrade - and I am in the slow ring, so I have not been offered 10525 yet, and when I do the slmgr commands, it looks like mine is 10240 retail and permanently activated. But, mine is receiving insider builds still, and that's the difference.
I have read here both ways regarding the keycode - some have gotten generic and some seem to have gotten unique. Could be the difference between OEM and Retail upgrades. I guess the telltale sign will be when 10525 is released to slow ring, and then to general public. You should not be seeing it until general release. And, since you are no longer receiving tech previews, I think you are fine. That computer is linked to your MSA, which is why you have the option to opt-back-in again. I think you're okay.