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hi AB. I'm Greg, an installation specialist, 10 year Windows MVP, and Volunteer Guardian Moderator here to help you.
Normally you'd have Downgrade rights from one of the higher version but not both. Those are also administered by your PC maker so I'd contact yours to ask to exercise your right to change back to the higher version.
If they confirm you have a WIndows 10 license then following the gold standard Clean Install in this link which compiles the best possible Install of Windows which will stay that way as long as you stick with the tools and methods given, has zero reported problems, and is better than any amount of money could buy: http://answers.microsoft.com/en-us/windows/wiki...
Preinstalled WIndows has a Product Key embedded in the BIOS chip so if you hadn't been on Windows 10 long enough for it to convert to the Digital LIcense used for most activations, you can read the key by installing ProducKey from http://www.nirsoft.net/utils/produkey-x64.zip and look for the OEM-BIOS key. That key may work if you know it's for Windows 10 and not Windows 8.1 or 8. If there isn't any OEM-BIOS key then it isn't a branded PC with factory install which are all that have Downgrade rights in the first place.
If you need further help to sort this out contact Microsoft Support phone or chat options here:
https://partner.support.services.microsoft.com/...
I hope this helps. Feel free to ask back any questions and keep me posted. If you will wait to choose if I solved your problem, I will keep working with you until it's resolved.