Okay, so after having not played the game for some months, I replayed it again tonight, and guess what happened?
That's right, the unskippable intro bug is back again, as always, and once again, the registry key which I had manually set to disable the intro (which I have had to do multiple times now) has somehow magically undone itself yet again, even though I never opened my registry again at all whatsoever since the last time when I had to reset that game registry key for this fundamentally broken game.
Contrary to some of the bogus counter arguments given to my point: there is nothing whatsoever wrong with my OS or my system or my UAC settings or any of that kind of stuff. Trying to blame those things is a red herring and an attempt to scapegoat the issue of this game-breaking bug onto things that actually have no relevance to it whatsoever.
I am using an official version of Windows 10 and official GOG version of HOMM 3 Complete. There is no monkey business going on here that would lead to such a bug occurring were it not to be a bug that is indeed & in fact infesting the official version of the game itself.
This is something wrong with the game itself that is causing it to change its registry key values on its own, which therefore as I said previously, and I again now re-emphasize the points:
1) GOG desperately need to patch this bug out of the game and also
2) This problem is not actually "solved," even though the OP has inaccurately marked it as being solved, because changing the registry value is not a permanent solution, since the game constantly undoes the registry key value change on its own for no logical reason.
And I haven't seen anyone offer any solution on how to prevent the game from continuing to do that, ergo this problem definitely remains 100% unsolved as of now in January 2023.
As for the counter-argument that it's not game-breaking because the intro ends eventually: I beg to differ. This bug is one of the most aggravating things ever in a game, and it makes the game totally unplayable since one feels very disincentivized to ever run it in the first place knowing that this problem is going to keep reoccurring forever (or until GOG patches the bug, like they need to do, so that it no longer exists in the patched version).
And it also makes the game unplayable because it's almost impossible not to ragequit out of the unskipple intro (via ALT TABBING and then manually terminating the game from the OS) after you have been a victim of this bug dozens or hundreds of times, and after you have manually reset the registry key many times, only to have to the game metaphorically spit in the player's face by automatically undoing that tedious manual registry editing work.
Likewise, time in life is very valuable and therefore it is not to be wasted endlessly & repeatedly ad infinitum waiting out this very long & very aggravating unskippable intro for all of eternity, which ought not to be ever occurring at all, yet it keeps re-occuring endlessly. And time in life is also way too valuable to be endlessly locating and then resetting the same registry key that you've already reset multiple before.
And if GOG doesn't want to track down this bug in order to eliminate, then at the very least GOG needs to patch the game so that the intro can be skipped with the press of a key (i.e. the ESC key), and that method to manually skip the would need to work always, 100% regardless of the status of how the game has automatically misconfigured its own registry keys.
EDIT: I realized I forgot to mention that I have manually went back to the "FirstTime" registry key tonight after making this post, and sure enough, the game has, on its own, without every being told to by any computer user, changed its value back to "1," even though I had manually set it to "0" many times before.
Post edited January 21, 2023 by Ancient-Red-Dragon