You have the opinion of Rava in the Talmud that one is liable for idolatry only when he accepts the idol  as his god. Abyee disagrees with this but the law is like Rava [as is always the case except in 6 specific cases where the Talmud says the law is like Abyee.][Sanhedrin 61b]

I had thought that perhaps the idea of "accepting as ones god," means to be initiated into the cult of that particular god. But my learning partner pointed out that this is unlikely. It would mean that doing downright straight forward idolatry would be not guilty as long as one has not become a devote. That is, one could walk into  the temple of Zeus, and bring a sacrifice with intension to gain some benefit [like rain (as was the original idea of Zeus before the Greeks elevated his status)], and still not be liable as long as one has not been initiated into the cult. This seems very unlikely.

So far as concerning idolatry I am still in the beginning stages of collecting information. But so far it looks to me that to be liable there is no need for a physical object. E.G. lets us say that some archangel comes down to earth  perhaps even the particular angel that the ancients associated with the name Zeus and this angel appears to a person and the person bows down to it. Would this be liable?

At this point it seems to me the most basic idea of idolatry is the worship of any being besides the First Cause in order to get closer to the First Cause or to gain some benefit. But this benefit has to be not in a natural way. There has to be some idea of this alternative being has some power over some aspect of the world or human life that is beyond normal physical reality.