Is it true that the first several episodes of TOS were incorrectly slotted in terms of production? Is 'Where No Man Has Gone Before' the official first ever episode?
I'm not sure what you mean. If you mean that the episodes were not aired in production order, that was common for the era. Most shows were made specifically so that the episodes could be shown in any order, to give the networks more flexibility in scheduling. So it can't really be called "incorrect," since there was no real "correct" order.
"Where No Man" was the second pilot, thus the second episode made, and the first one with William Shatner in it, as well as the first with James Doohan and George Takei. It was the third episode aired. The first non-pilot episode produced was "The Corbomite Maneuver," which was the tenth episode aired and the debut for DeForest Kelley, Nichelle Nichols, and Grace Lee Whitney.
What with the original pilot 'Cage' left on the scrapheap because the studios wouldn't accept it given their humongous heads not being 'conceived' well from the public perspective.
Actually the execs were impressed with "The Cage," but it didn't really tell them what they needed. According to
Inside Star Trek by Solow & Justman, Desilu pulled out all the stops to make "The Cage" as high-quality and cinematic as they could, because the studio had never attempted a production of such magnitude before and needed to prove it was capable of it. But that didn't serve the needs of a pilot, which was supposed to be a more typical episode in terms of content and budget, so that the network could estimate how much a full season would cost to make. So NBC asked for a second pilot that would be more representative of a normal episode. Essentially, the first pilot was to sell Desilu and the second was to sell
Star Trek.
Also, contrary to the myths Roddenberry spun later, part of the reason NBC rejected the pilot was because the cast was underwhelming -- and because it was all white. Networks at the time had recently seen the results of studies showing the buying power of minority viewers, so there was a push on to make TV shows more diverse. Roddenberry liked to claim later that he pushed for an ethnically diverse cast over the network's resistance, but in fact the network asked for diversity and "The Cage" totally failed to deliver. Aside from one Asian-American extra in the transporter room, the only supposedly "ethnic" character in the cast was Jose Tyler, who was played by a decidedly non-Hispanic actor and whose name was never spoken in the pilot anyway. So NBC asked Roddenberry to try again with a more interesting and more diverse cast.
I'm not surprised Jeffrey Hunter resigned from the project as the studios couldn't decide where to go from there.
That had nothing to do with it. Apparently he stepped away because he didn't want to be associated with science fiction, a genre that was not considered respectable at the time.