Where did you say you already Upgraded to Windows 10? I went back and looked and I dont' find it until you just now wrote it and said "like I said."
If you upgraded to Windows 10 and saw it was activated with a Digital License then it will still be there if you reinstall WIndows 10. You might need to contact Microsoft Support to revert to it, but not always.
You also just now said that in the Spec .pdf you sent me it says it downgrades from Windows 10. Where? I quoted all it says about Windows in the specs under "Preload: Windows 8.1 DG Windows 7 Pro 64" which clearly says it is for 8.1, not 10. Nothing is said in any specs you gave me about Windows 10 for this PC. In the Lenovo information pages on Downgrade rights I gave you (which are written for consumers and not technical) it refers to Downgrade rights from either Windows 8 or 10, never both. I have handled literally tens of thousands of activation cases in forums and have never heard of both being downgradable.