1. The Guardian of Forever doesn't bring people back to life. I think. Could be some obscure lit.
The Guardian of Forever can do whatever the writer wants it to be able to do. "Terra Firma, Part II" canonically established that it's capable of extremely powerful matter manipulation, for instance.
2. Khan was blown up. No magic blood.
Unless McCoy drew some blood when he was in sickbay in "Space Seed."
