I don't remember where I got all the resources for that version, but I believe it's supposed to be GOF 2.0, plus the 1.5b patch. However, looking at the HeroDescribe.txt file that contains the character selection, it does not look correct, so I am not sure where that came from. Anyway, I just replaced that file with the GOF 2.0 version, because I don't see the 1.5b patch .zip has a replacement file for that, and neither of them match what I had in the Itch upload.
Update GOF 2.5 and you should be able to select other characters now. However, from what I have read, I don't think GOF 2.0 and GOF 2.5 are reliable and I don't believe they were ever "finished" and complete either. They also removed much of the material and gameplay that made GOF 1.2 such a good alternative; they stripped out much of the GOF work when they made 2.0 and 2.5.