E1
Threepio was a 3PO. Until he wasn't.
E2
We can't say a whole lot about Anakin's father with any certainty. However, we are certain that the current explanation - as it stands - is suboptimal. Let's take a look at what the Prequel Trilogy and the reference books have to say and see if we can't come up with a more satisfying conclusion.
E3
Let's discuss Naboo design philosophy and their engines. Someone decided that the N-1 starfighter would be very eco-friendly. You would never find a plastic shopping bag drifting through their swamp. This extends to their clean-burning spaceship engines.
E4
Valorum's shuttle is an Eddicus-class. Not much is known about this one, and for good reason. This, a boring ship for boring people, had escaped from the lore.
E5
Recently, we discovered a gulf of knowledge. One of our latest videos talked about protocol droids. Specifically, it was about TC-14, and the 3PO series in general. This naturally involved a mention of C-3PO, but only as an example of his model. A lot of the comments on this video were identical.