No one has discovered a real license for Windows 8.1 Embedded Industry Pro outside of evaluations or via MSDN resources.
It isn't listed as an available SKU in public databases.
No evaluations or references to MSDN. Not familiar with that.
No, you can't use it freely without permission.
You might find some aspects not functioning properly.
No, I don't use Windows 9. It's an outdated operating system no longer supported.