Okay, first off, bitterlad, don't double post. If you have more to add and no one else has posted yet, use the modify button on the upper right corner of your post. As I'm not a mod, this is a friendly warning from an older member.
As another friendly warning, one word posts aren't allowed either. I doubt including a quote from a previous post will excuse a one-worder.
Now then, to answer your questions.
You mentioned a shadow form. Would it be too much to consider that in her "Shadow Form" she could possess other peoples shadows? (Like Midna from TP.)
From what I've seen of the games, I doubt it. Perhaps "shadow form" was the wrong choice of words; "ghostly" or "ethereal" would have been better.
Also, I wouldn't say that Midna possessed Link's shadow; it was more like she assumed a shadow form and was just hiding in Link's shadow.
Also, I've read somewhere that when Veran possesses someone, the victims skin turns a strange teal color. Is this true? And if it is, then why does no one notice this?
It is true that Veran's victims take on a darker skin color; teal, I suppose. It difinitely is some kind of blue. As for why people don't notice this, it could be part of Veran's magic. Or it could be that the teal (or blue) color is used to show the gamer that the person is possessed, but the victim doesn't actually change color. After all, if you're possessing someone, you don't want to give off a blatant sign that something is wrong with the person you're possessing.
And why would you revive a sacrifice instead of the one you sacrificed the person for?
I do doubt that Twinrova would resurrect Veran or Onox, but it's possible that someone else could resurrect them.