I agree with SGS and Bluish, I don't think Garuda developers are supporting your specific use case. That's the beauty of Linux, developers can choose what use case they want to support. Garuda has been optimized very well for the use cases chosen by the developers.
Garuda has its own objectives and unfortunately for you it seems yours is not on the list. Just like my own use cases are not on the list of some other distros than Garuda...
Perhaps it is not worth repeating, but I will anyway: I think this will work badly.
USB 2.0 is too slow for this kind of system. This is not an insignificant detail; USB 3.0 is ten times faster than USB 2.0, and a USB 3.0 bus speed is still a higher latency than you would get with a proper drive on the metal. If you get this installation up, it is going to be a dog.
Between taking proper weekly updates and Btrfs snapshots, you will be taking a lot of read/writes to the flash media and it will not last long. A system that does not call for such an aggressive update routine would be a more practical choice if it is going to live on flash media.
If you insist on doing this anyway, you will have to go into your native BIOS menu and disable secure boot to be able to bring up this system. Have you done that?
Please explain what you mean by this (what system, what partition) and list the directory path if possible.
You have informed the boot repair tool you are using the MBR partition table. If you have an EFI partition you will have to select ESP.
I understand you want to create a Persistent Arch system on a USB drive and you selected ViirtualBox as a Linux system to accomplish that.
I regret to inform you that this is not possible. If you or anyone else thinks I am wrong, provide proof.
You have been told several times that this is not working…
Your alternative require 2 USB drives:
Use your current OS (WinOS?) to create a bootable Live ISO of any Linux distribution you want. Boot with that and install the system to the 2nd USB drive.
A special program that is developed for this exact reason is alma, available for archlinux and on Github.
I have used alma successfully and I strongly suggest it for this type of project.