Clean-install Windows 7 after the Win10 revert option has expired?

Hi.. I see there's a fairly recent thread called "Downgrading to Windows 7" but that's not applicable to me. I haven't got the "go back to an earlier build" recovery option. So, here's my situation:

HDD 0 is my surfing C drive, and has Win10 - that Win10 being a July 'upgrade' of Win7.
HDD 1 is a non-OS drive. I want to use my Win7 disk to create a new OS from scratch on this HDD 1.
HDD 2 has an earlier Win7 with no internet access, and I want that left untouched. So let's ignore HDD 2.

Now, I gather that Win10 has might have 'locked on to' my MS licence, and may have revoked use of the product key for Win7. So my questions are these:

1: If I go to all the bother of installing Win7 on HDD 1, will the product key be accepted?

2: If the answer to 1 is 'no' then what if I totally wipe Win10 from HDD 0, and then try installing Win7 again? Might I be left in a situation where I can't have Win7 on my PC, and have lost my rights to Win10 as well?

The Windows 10 upgrade did nothing to your Windows 7 product key, it remains just as valid to use in any legal installation as it always was. HOWEVER it violates the End Users License Agreement to have the Windows 7 and Windows 10 upgrade resulting from that Windows 7 license installed on the same computer at the same time. Thus it also violates this forum's rules to discuss how to do it. You have 1 license/product key for Windows - that means only one installation of Windows is legally allowed from that license/product key, Windows 10 or Windows 7, not both; even though only your honesty is preventing you from using the same license for both the Windows 10 and Windows 7.

If you choose to purchase a second license for Windows, then you can see here for more information:
Windows 10 - Dual Boot with Windows 7 or Windows 8 - Windows 10 Forums

NavyLCDR said:

..... HOWEVER it violates the End Users License Agreement to have the Windows 7 and Windows 10 upgrade resulting from that Windows 7 license installed on the same computer at the same time. Thus it also violates this forum's rules to discuss how to do it ......

Ooops, sorry about forum violations. Minefield alert... guess I'm one of the folks who didn't read the EULA properly!

I think I'm safe in asking, though: if someone were minded to ditch Win10, and just have Win7 on their PC... thus simply rolling the clock back to how things were a few months ago... then presumably that's within both the letter and the spirit of the law?

(And here I mean both MS EULA law and also 10Forum regulations.)