JLArranz said:
Afaik, x64 mode ("long mode") cannot run 16 bits software because it lacks the Virtual86 mode that 32 bits mode has "inside", so it's a hw constraint (that said I've had Vista 32 bits and it run 16 bits sw w/o problems, but I have never used 7-32 or 10-32 to see, because 16 bits sw isn't way enough reason to limit my computers to 3.5 GB). Both x32 and x64 modes are like "buildings" (hw/sw structures like virtual memory pagetables etc) that the OS must build during boot up, different buildings so an OS cannot freely jump between the two.

As for sw, Vista moved all around, likely to do a "clean" or "uniform" new platform for both 32 and 64 bits products, instead of introducing a very different 64 bit standard and developing both at the same time, or carrying some legacy flaws to the 64 bits world, and created a jump. But successors from 7 to 11 are still following its same "rules" and Vista drivers might work in some cases.

Later "jumps" like UEFI or enforcing SHA2 (the latter "killed" XP and Vista usability for the net at the same time, although Vista has more SHA2 than XP) have been created to increase security. A Win8/8.1 driver has more chances with Win 10 or 11 because some latter features started there (for example in my Win10 motherboard I can select "Windows 8" for it or higher, or "Other OS" for Win7 or lower, this setting has other embedded ones to select or not CSM and its options).
Mostly true; the "change"was pretty much between VISTA and Win 7. I bought a "NEW" laser (monochrome) printer about a year ago (after a 30 y/o H-P LaserJet 4P finally died) and it still "shipped" with Win 7 drivers! The manufacturer (XEROX) did have the Win 10 drivers (if needed; some Win 7 drivers were still good!) I USE it wired through USB, but it is supposedly usable through WiFi, and I fear it might not be "Windoze 11" compatible. But much of the hardware support and documentation was written when the main Windows version was widely available, and doesn't mean it won't work with a later version of Windows, although updated software MAY be able to support tit's features better. For\the most part, Win 10 can use Win 7 and later drivers, but hardware sold for VISTA, XP or earlier doesn't even have the hardware in it's "library" or database. (Case in point: I have an C, ITOH [dot matrix] printer. Even XP from Microsoft didn't include drivers for such an "old' (think DOS or Apple ][+ days!) printer, but I can still use it with Win 10 if I need to. It IS a game Microsoft and the computer manufacturers play, they always win (by making perfectly good and functional hardware obsolete) and the users ALWAYS lose, by the need (or at least perceived need) to buy a new computer. upgrades of versions often installed such "undocumented" software to enable use of hardware not natively supported by Win 7 and above.