Bad Export for You: 3. Not necessarily because of the inflated difficulty itself, but because the lowest difficulty setting in the overseas versions, Easy, includes Easy-Mode Mockery that cuts out the last two stages of the game, while the Japanese version's equivalent difficulty level, Normal, lets you play to the very end. In other words, you're punished for playing a non-Japanese version. Also, the Japanese version's Easy difficulty, which still lets you complete the entire game and would've been the overseas versions' Easier Than Easy difficulty, is removed altogether.
What Could Have Been: Pre-release screenshots show that Streets of Rage 3 was originally going to feature a section where the heroes ride motorcycles.
Amongst other things, it appeared that Adam and Axel were originally called "Wolf" and "Hawk" respectively.
The fan remake:
Ascended Fanon: Prior to the release of version 5.0 of the remake, it was very common for newcomers on Bombergames' forums to ask for its release date, to the annoyance of every regular. One such lucky user was teased with an animated GIF of one of the basic enemies, its name the same as the user in question's forum handle, getting sent flying Super Smash Bros. style into the ocean by Blaze and the massive medieval Banhammer she was wielding. The image was enough of a hit to warrant a special playable event in its honor once 5.0 came out, sans the name of the user that spawned it.
Fanwork Ban: Sega didn't take kindly to it and threatened to sue the developers if they didn't remove it from their site.
Keep Circulating the Tapes: Like many other fan projects that were axed by the copyright holders but had reached a complete release, you'll be sure to find Streets of Rage Remake V5 around the net years from now. Quite a few people, due to the timing of the C&D order, believe this may have actually been Sega's intention all along; give the game time to circulate, then send the C&D to keep their shareholders happy. Not to mention the order generated plenty of publicity, making many aware that the remake existed to begin with.
According to reports (like here for example), Rudra was originally conceived as an April Fool's joke wherein someone designed her and placed her on the SOR forums, touting her as Shiva's sister—except, a lot of fans didn't get the joke and thought she really existed. From that point she was drafted into the remake with intentions of actually making her and Shiva siblings, before the development team changed their minds and took her in a completely different direction, resulting in the Rudra we know from the fan-game's final draft.
Version 4 of the remake had Super Shiva, an incredibly difficult final boss that was on a strict time limit. Not only was Super Shiva the toughest enemy in the whole game, but you'd automatically got a bad ending if the time ran out, which caused the entire level to self destruct. The developers kept the time limit final boss idea intact, but it was used only for one of the paths in the game rather than the only path and Super Shiva was cut.
During development of the remake, developers toyed around with the idea of allowing the game to be played online. However, the team simply couldn't get a proper net code implemented on time when version 5 was close to release, so they decided to make the game local play only.