OK, this is now more a technical experiment, but may be useful getting it done properly and fully working some time in the future.
I have been copying a whole Windows 10 Pro disk into another hard disk on an USB disk enclosure with EaseUS Partition Master.
Then when trying to boot from the USB enclosure hard disk, the first thing noting to be missing was the activation of the booting partition, so, I did it with Diskpart and it seemed being valid on the Disk Management.
The second obstacle were the wrong BCD definitions on the USB disk Boot, but they were corrected automatically for/into C: after some reboots.
Next when booting from the USB enclosure hard disk it was leading to BSOD INACCESIBLE_BOOT_DEVICE, and after the automatic reboot once again to the same. But the second time automatic reboot did lead instead to Error 0xc0000001 and gave the chance to go with F8 to the boot definiton alternatives, and choosing there F4 the boot did lead actually all fine into Windows 10 Pro, but just in Safe Mode! But, on all the next Normal reboot trials getting once again to the INACCESIBLE_BOOT_DEVICE BSOD reboot procedure etc. as above ...
Now the question is, what is missing or wrong in all this, not getting the USB enclosure hard disk boot done straightaway in good order?
So, as a conclusion
- USB disk partition active OK
- BCD on USB disk correctly for C: OK
- Mounted Devices correct USB disk for C:
- boot into Safe Mode all OK!
- same behaviour with or without the internal hard disk in and operable
- what's still wrong or missing for Normal boot, INACCESIBLE_BOOT_DEVICE???
Thanks for any hints to be checked!