Windows 10: installing product key for windows pro during update errors ?

do Update Errors Compromise a Product Key Change? - I purchased Home version Product Key instead of 10 Pro for a pre owned laptop, having zero windows 10 experience and I am Done with the experience of Learning to Downgrade this ^#&@!!* I Purchased another Key Pro this time So should I attempt the changing of the Keys? Im pretty sure I brought on these Errors monkeying around they've changed 3 different times through out this whole debacle. I do have the Codes for reference if need be.

:)

 

Windows 8.1 pro + WMC key activation

So it will be fine installing 8.1 pro with a KMS key, then switch to my 8 pro key and it will activate ok?

Maybe a daft question but why can't you just install 8.1 pro with the 8 pro key, or is it different keys for 8 and 8.1? seems silly when 8.1 is a free update anyway.

 

Windows 8.1 pro + WMC key activation

This worked for me last time with a Win 8 key.

Install Windows 8.1 and enter KMS key during setup. Once in windows change product key to my Windows 8 key. Go to add features and enter my WMC add-on key. Drink a beer to a job well done.

 

Will a Windows 7 Ultimate key activate Windows 7 Pro?

I've tried the opposite, was installing Win7 on a friends comp, my copy of win 7 (home premium) and his key (pro). When I entered the key, it gave me an error regarding versions. Skipping the initial key input also lead to a version error thing when Windows booted up. One big thing I noticed when I did that was it didn't let you choose the version to install if you skipped the key input. In short Vista lets you use whatever disc to install, 7 doesn't.