New
#11
Yes.
Well, it deletes the markers to the information (Master File Table or File allocation Table). Until the old information is written over, it's still there - it just takes special software to retrieve it.
No. When you install Windows 10 on the same computer it will calculate the same Hardware ID as the previous installation of Windows 10 (calculation based on hardware installed [mostly the motherboard] not on information stored on the hard drive). The Hardware ID is sent to Microsoft activation servers, where the previous Hardware ID and activation was stored when you upgraded. When the activation server finds your matching stored Hardware ID, it will return the activation - if the version of Windows 10 also matches.