2. Will not be a problem boarding card you use going through security, if not used it will be a "no show" or "late at gate". System is not capable of doing the reconciliation you are thinking of. Main function is to ensure boarding pass is genuine.
Does that mean that if flying with only hand luggage, I could (only theoretically, mind), pay for a cheap flight from STN-DUB (for which I get a genuine boarding card), and create a fake boarding card from STN to somewhere expensive like Tenerife. KUL might be pushing it a bit far. Present the genuine STN-DUB boarding card to security.... and then present the fake STN-TFS boarding card at the gate - (assuming there are spare seats) ? Mr Plod would of course be keen to talk to me if I got caught !