I had Win 10 Home 1809. I read that Sandbox can run only on build 1903, So I upgraded to 1908, and installed sandbox with this guide It didn't work, and I kept getting 0x80072746 error.
You will be unable to enable Windows Sandbox on your Windows 10 Home installation. The unofficial patch to allow it on Windows 10 Home doesn’t actually work.
I then read that sandbox could have actually worked on build 1809.
What you read was absolutely false. Windows Sandbox requires Windows 10 version 1903 or newer. Windows 10 version 1903 is build 18362 which of course newer than build 18301.
Windows 10 Pro or Enterprise build 18301 or later (currently not available, but should soon be released as an Insider Preview build)
What are my options?
Your only option would be to upgrade to Windows 10 Professional
Should I revert to 1809 using windows recovery? Will it then work?
Windows Sandbox cannot even be enabled on Windows 10 version 1809.
Is it possible my Intel bios doesn't have virtualization enabled and that this is causing the issue? any way to check that right away? I didn't see anyone suggesting to check that when people reported this error.
The error has to do with the fact you are running Windows 10 Home instead of Windows 10 Professional. While it’s possible your processor doesn’t support VT-x, most Intel processors actually do support it, but based on information you provided is absolutely not the reason your unable to use Windows Sandbox.
The patch to allow Windows Sandbox on WindowsApps 10 Home absolutely does not work. Windows Sandbox is only a feature of Windows 10 version 1903 and newer. Windows Sandbox absolutely can be enabled on supported editions of Windows running on hardware that supports all of it’s requirements.