Locked out

No, it will not block the BIOS area.

I have just been informed by the tablet manufacturer that the only access to the BIOS is via a keyboard either pop up or plug.

Does this mean the tablet is now useless? Or can you offer any advice?

Regards

The USB ports should work without issue during the boot process. They may be disabled once the OS boots if you disabled them in the Secure Lockdown settings.