If VirtualBox stuck on Saving state, your machine is in the hung state. Kill the VM via the Command Prompt, disable Core ...
I don't think Virtualbox has a UEFI option, so I think virtualbox is (rightly) booting legacy. But still it can't boot from that ISO I just tried VMWare Player I notice that one can choose UEFI or not ...
If you find yourself with a mismatched VirtualBox and VirtualBox Extension Pack release, such that VirtualBox itself cannot resolve, Jack Wallen shows you how to fix this from the command line.
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