I don't think it's currently possible with Windows 7. Windows 8 and later would work as they included bootia32.efi. Some Linux distros with bootia32.efi would also work unless special drivers are necessary. Maybe check whether your device supports legacy boot/CSM?
Maybe it's possible, if users can boot XP in UEFI using Longhorn files, Windows 7 using Windows 8 can work too. But I don't have time for this research
Maybe. If you use Windows 8/10 bootloader, integrate proper video drivers and remove legacy VGA driver from install.wim