According to the man himself the reason to do the first episode as4 as opposed to 1 was because in the time of 1975, a scifi was questionable to be a success. In the story timeline of 9 episodes, he wrote the first one as mostly character and location development, he said which is typical of most long detailed books. As such the first episode would have been a slow moving movie with little action. So, he said he jumped into Episode IV or the second generation Skywalker, Luke because it would start out with the ending of the clone wars. All he needed to do was establish references to Anikan and leave who he was a mystery. IF the first release was a box office success, he could complete 5 and 6 and then go back and do 1, 2 and 3. By the time he was into episode 5 he decided to re write 6 to include all he originally intended to include in 7,8 and 9 in the script of 6. Consequently there will never be a 7, 8 and 9.
Yesterday, I completed the animated Clone Wars and listened to George Lucas comments on it. Clone Wars was an authorized separate writing for the Cartoon Network but when Lucas saw the first screening for his approval, he wanted to take it to the big screen as a series to fill in the gap between episode 2 ( the start of clone Wars ) and 3 begins with the end of the clone wars. So far only the first of that series has been converted to theatrical release. It was not well received at the boxoffice. There was a lot of misinformation as well regarding it's authenticity. But, George Lucas and many of the actors of Star Wars 1 and 2 were used as Voice actors in the CW series.
I have now completed the new BD release up to episode IV. I have completed the director comments too and it was the best yet describing how they made the original and modified / upgraded much of it for Blu Ray.
I didn't know that when they started shooting Episode 4 they didn't have Blue Screen and the first saber fight was done with film double exposure and can never be updated. After that they started using blue screen so that the base film with actors can today be recomposited digitally with higher detail CGI. They made some mistakes with R2D2 when they first started using blue screen as he had some blue striped painted on him and these keyed out in the fighter scenes. Before they figured out how to fix this, they ended making those shots in B&W. Few people noticed this.