Re: The prefix number
It can't be too hard to change the prefix code. Spock considered Khan capable of doing it. He probably would have, too, if he had known about it.
Khan who was a genetically-enhanced superhuman. After all, Saavik was herself highly intelligent, and she had no idea what Kirk and Spock were doing until the admiral explained it to her.
"I've sworn an oath to serve and protect the United Federation of Planets- an oath I will fulfill with my dying breath- for in my heart, I remain a creature of duty. I am Romulan." --Captain Sran, USS Naptown