Hermes is the greek god of theives, travelers etc. He is the messenger of the gods. Iris is sometimes known as another messenger, but that is false. She is the goddess of the rainbow. They mistaken her as a messenger because when you throw a golden drachma (the currency of the gods and demi-gods) into mist, you say who you want to contact. This does not make her a messenger, she is like a telephone operator.
No, the Greek gods are myth.
Greek and Roman gods are myths
That they are Greek gods and goddesses. No, at least not in Greek myth; they do not unless they desire to.
Greek myth does not say.
In Greek myth, yes.
Zeus was the King of the Gods and Goddesses in Greek Myths.
Myth
Zeus was.
There are twelve official greek gods.
Mount Olympus was where the Greek gods supposedly lived
There aren't any powers the Greek gods could not have called upon in myth.
Usually, yes.