I think this would just be asking for trouble considering how often your license plate gets read.
Where this stuff is just automatic, and I imagine it simply gets flagged. So the police officer themselves don't even have to notice it, and instead they're alerted to it. Whether they pull you over depends on whether they have better things to do or not.
Absolutely! I don’t know for sure, but I would guess that nearly every police car in the US (local, county or WSP) has plate recognition software installed. Just like you said, the officer probably gets an alert for EVERY car that has any outstanding warrants, tickets, expired tabs. I’ve had shirttail relatives pulled over for this very thing. IIRC, these systems were pushed out after 9/11 by the newly formed Homeland Security Administration, essentially funding from the feds and free to all. I think I remember an NPR story on how this technology hasn’t caught a single terrorist, but instead essentially catches those at the lower end of the socioeconomic ladder, struggling to make ends meet, on minor technicalities.