I think the Airmotiv 4/5/6 were iterations of the same basic active speaker. Great reputation for performance at the price point. Emotiva discontinued them and only makes passive speakers now, I think. I also think the Adam 5 are very similar to the Airmotiv, and I have even read that they may have been manufactured in the same factory in China, with different branding - though I have no way to verify that.
Yes. I think the 4 or 5 was first, without an S (not sure)? Then they did some kind of slight upgrade after a few years and added the S designation to the model series.
And yes. There was a Chinese speaker that appears to be the same as the original Airmotiv and may have been first. Whether or not Emotiva asked for any changes to the design from the factory, I don't know.