Why would you want that first one? 馃え
You can already choose whichever gender you want for your character.
That worked? For me I opened a Virtual Machine, downloaded a fresh new game, then copied one of the save files I had and only that, still didn't work. Nameless tells me I shouldn't mess with save files and I still can't redo my choice.
My first guess was that there was like some value in the log file of the save that it would check to see if you already made a choice, but if your method works I don't really know what is going on.
It sucks tbh, like this is supposed to be a wish fulfillment type of game, and when I saw I couldn't go back and pick a better option.. it would be cool if it were some more serious game, and it also doesn't help that it takes a LONG time to get to that point in the game, it kinda just instantly killed my boner...