Yes they are. Both angels and demons can go into a human body.
Yes they are human angels and some do consider them self as good and bad(fallen angels)
People cannot be angels...ever.... if you think you are then you are a damned hypocrite running away from your shadow self. Just stfu please before you hurt people with your false promises of love and light. Maybe you are feeling earth's vibrations up your arse because that is where your head is making it impossible for you to distinguish between real and fake light.
Those are the dark fallen angels you are talking about
The definition of Angel is messenger. Have you ever given someone information that you know didn't all come from you, but it helped change the life of someone else for the better? In that moment, you were the messenger. I believe that at times God works through normal human beings for the benefit of another human being. And in those moments they are considered angels.