The free upgrade to Windows 10 is actually intended for Microsoft for users of assistive technologies that are widely used by people with disabilities. But because there is no verification at all, everyone who uses assistive technologies features or not, can take advantage of the moment of this free upgrade Windows 10.
Previously a free upgrade to Windows 10 in this way is limited to 31 December 2017 only. But Microsoft extended this opportunity by backing the deadline until January 16, 2018.
This means there is another chance if you want to upgrade Windows 7 / Windows 8.1 to Windows 10 for free. If you want to upgrade to Windows 10 with Windows 10 Update Assistant method, Windows10Pro has already created the tutorial.
You just Download Windows 10 Update Assistant and run the Wizard.