Android Re-Installation Question

I have a client with a "bricked" Motorola G6 Phone (e.g. MotoG6). The client can't remember the PIN code and doesn't recall the Google Account associated with the phone.

The phone number is long gone.

Is there a way to reformat this so that it's reset to the factory standards? I've done a half-dozen or so YouTube tutorials, but all rely on the previous Google account to be known.

Is there a way to put the Android OS on an SD card and, for all intent and purpose, "start over"? I've seen the term "root"... is that the same as reinstalling the operating system for Windows (e.g. "nuke and pave")?

Thanks!