I mean . . . the fact that there was a revised 4th draft (at least two of them I know of, in point of fact) by it's very existence implies that of an unrevised one, else what the hell does one think is being revised? Indeed, through the arcane wizardry of basic mathematics, one might even infer the existence of not only a third draft, but a second AND first one too!
And yeah, as has been stated there were a LOT of draft revisions over the years before a single frame had been shot, and there were more done later both during the shoot, and later in the editing process. Mark Hamill famously recounts not knowing he was playing a character called "Luke Skywalker" until the day they shot the detention centre scenes, as the scripts he'd had up until that point had all had him down as "Luke Starkiller", None of this is new information. I mean the fact that that blog in the link hasn't been significantly updated in 6, going on 7 years should be a clue.
I will say though, if one wants to get a reasonably definitive overview of the making of the first movie, from conception, through all the major drafts, pre-production, shooting, post-production, release and response, I'd recommend reading J.W. Rinzler's 'The Making of Star Wars: The Definitive Story Behind the Original Film'. Yes, it even covers the part mid-shoot where George decides to kill off Ben on the Death Star instead of have him survive to the end, where he was scripted to do little but stand around looking worried.
As for the way that decision shaped the later movies; most just in that it resulted in the creation of Yoda. Presumably he would have eventually been killed off in the 3rd one, one way or another. But then which part of the multiverse are we talking about here? The one where the movie is only modestly profitable and the 'Splinter of a Mind's Eye' script is the even lower budget follow-up? Or the one where George doesn't get burnt out and goes ahead with the full 12 movie plan, well into the 90's in which case ILM is probably too busy to do either Abyss, Jurassic Park, or T2, and the history of digital VFX gets rewritten again?