If you notice on some scenes of the Avengers, whenever Thor tries to take Loki back to Asgard, you can see how his eyes are green as he fights himself. On Stark Tower, while stabbing Thor, look closely and you can also see Loki shedding a small tear.
My heart. "That Loki died a long time ago." Unfortunately true. That Loki died in the weapons vault when he discovered he was a Frost Giant.<<<NOT OKAY <<< NO. That's not true. I believe that somewhere, deep inside, that Loki is still there.
"Prince" is a title, but not a profession. Being a prince, he may also have a profession unrelated to public affairs. Most likely he is a scientist, or rather a physicist and engineer, specialized on spacetime anomalies. And also a traveller and explorer.