Q] Was this game region-locked?
A] Yes. This was the only Shinobi game for the Genesis/Mega Drive to feature this. For example, you cannot play the American version of the game on a European machine
and will get a message if you try. It is possible to get around this by using something like a Game Genie.
Q] There are some prototype screenshots on the back of the US version's box?
A] There are four images on the back of the box, two of which seem to be from a non-final version. There is a screenshot of round 4 which has different enemies vehicles, and there is also a screenshot of the round 6 sub-boss which shows a different background. Thanks to André Nascimento for this info. Another thing to note is that the cover art for the American and European versions of the game feature a soldier with a flamethrower -this enemy is not in the final game, but was in the original version.
Q] The credits state the series was "to be continued", was it?
A] Not exactly. Whilst there have been several Shinobi games released after Shinobi III, none of them continue the story of the Genesis games. Since then, Joe Musashi has only appeared in Shinobi and Nightshade, both Playstation 2 games, and even then he is a hidden character who is difficult to unlock. All of the other Shinobi games, such as for the SEGA Saturn and Nintendo DS, feature different main characters.
Q] Was this game available on the Nintendo Entertainment System?
A] There is a pirate NES version of the game, which is available on certain multi-carts.
It features many of the levels, but some were cut -for example there is no boss fight for round 3, and round 4 seems to be missing entirely. The collision detection isn't great and some of Joe's moves are difficult to do (like the somersault) or just missing entirely (the spider-walk). This pirate is also known as "Super Ninja 2". However this wasn't the first time a Shinobi game appeared on the NES...
Q] Was the Mega Drive version re-released?
A] In Europe, Shinobi III was re-released in 1995. Aside from having a different cover, the game is the same as the original release. A similar thing happened in Australia, as the game was re-released as part of the "Gold Collection".
Q] Is it possible to do the 6 button controller code on other versions of the game, such as the Playstation 2 or Xbox 360 versions?
A] I don't think it is, because those versions have no way of letting you hold down the "mode" button.