It is there to simulate having weight on the pylon. I’m guessing that they removed fins for convenience.
It's not just a dummy missile afaik
It's blue and it has a seeker so it should be some sort of onboard guidance for training purposes.
As to the missile that it is simulating, I'm not fully sure if it's a PL-8 or PL-10, but it's big deal either way
Just a SRAAM training round.

