Does an Administrator-Defined Scan scan the mapped network drives? A. No, it does not.

Does Symantec Endpoint Protection scan USB drives?

Keep in mind that SEP autoprotect by default will scan any file on the USB drive if the file is opened, copied, moved or previewed. So if there is malware on the USB drive that would harm the computer, it will get detected once executed. You don't need to perform a prescan to be protected against malware on USB drives.

How do I scan to a network drive?

Locate the “Run full scan on mapped network drives” setting in the right-hand pane and double-click on it. Set “Run full scan on mapped network drives” to “Enabled” and click “OK” to save the changes.