I was thinking exactly this. To me it looks more like S&K 0525 was actually the next build of S3C 0517, that's it, they developed S3C first and it was continued as Sonic & Knuckles with the implementation of the lockon.
0525 is NOT Sonic 3C. The S2K 0524 S&K rom is exactly the same as this one. Ergo, it has lockon, ergo, it is S&K/S3B
We know, drx. What we mean is, this was probably the earliest version with lockon. If you remove Sonic 3 from the end (if you didn't notice it is seperately there appended to the end), the game has working content, though it is relatively fucked up. So, it's the natural evolution of what USED to be S3C :P
In other words, they developed S3C, then scrapped it and took what they already had and started work on S3B, firstly implementing the lockon but not rebranding it as S&K or making it work as S&K properly. Once the lockon was working they then started rebranding it for it's eventual release as S&K.
In Sonic 3C 0517, you can select Knuckles from the save data screen. However, in S&K 0525, you can NOT select Knuckles from the save data screen -- he is only available in level select.
They most assuredly did. Note that it is heavily dependant on Sonic 3 (which is final), so I have a feeling the character selection mappings were taken from Sonic 3, and were not 'split' yet, as with the code for bosses and etc.
How much "Sonic and Knuckles" code is actually present within the Sonic 3 Final ROM? Splitting S3 away from the 0525 proto shows that it's the final release, and since the version of S&K depends so much on S3, just how much data needed for S&K is actually present in S3 Final?
Not code, but pretty much anything that takes space from Sonic 3, namely the static data such as graphics (title screen, sonic 3 zones, etc). The code however is not shared, and should be entirely from S&K, which means the data selection was done on purpose for this build; which is why it seems weird the fact knuckles is blocked there, unless this build was done using a different "original" source than the one used for the last Sonic 3C build. The game simply won't load without sonic 3 because the code misses some data, I guess they chose to load the sega logo directly from sonic 3 too at this point.
Just based off an educated assumption, it looks as though Sonic 3 affects the S&K levels as well, in terms of some badnik sprites, level tiles, etc. Level tiles are garbled and badniks are also garbled or sometimes do not even display, though you can still hit them and they can hit you. Is this also being referenced from the Sonic 3 ROM? I don't know much about how this all works from the technical standpoint, though my curiosity is quickly rising. If I can find time in between school, work, and homework, I will definitely try to dive into the technical aspects.
I'd take anything you find using that savestate with a grain of salt. The savestate was made with Sonic 3 attached and it is expecting to find Sonic 3 in the rom. Having said that, I've tried similar experiments with Sonic and Knuckles, with an S3&K savestate loaded, and it was able to load the S&K levels properly at least, so... I honestly dunno.
Well the savestate is in the level select. It doesn't govern what the levels do when you click them. And, when you Start+A, it goes back to the level select and the S3 levels are still selectable (though crash), so it just seems like an early incomplete S&K to me.
Another note when playing the split Sonic and Knuckles 0525 - If you load Mushroom Hill Zone Act 1, Sonic will go through the motions as though you are looking at Knuckles hide the flashing ring area, but the level will dynamically change the starting point of the act to where Sonic would start in a standalone S&K build. I'm not sure if I typed that clearly enough, but I found that interesting. It's like MHz 1 checks to see if Sonic 3 is attached, and since it's not, it dynamically changes the starting point. I can't be sure if this is what it does, but an educated guess seems reasonable enough.
The Strange thing about this game, is if you die, you Respawn in Debug... I once went to SSZ A1 With Sonic and when Knuckles pushed the switch for the bridge, I ran straight across it a 'Accidently' Jumped onto the Spikes. I respawned in Debug. In FBZ I you are in Debug and Spindash pressing B and C you swap gravity, no? It does a simular thing here. I use the Spindash (Bare in mind I was pressing B and C, so I went in and out of debug) and I stop in midair and Sonic starts to Flicker all of his Sprites.... The Game also hangs up, but you can pause and press A to get out of it (Already Known). Gens+ users or have a Gens+ in Handy, I have provided a Download of the Glitch in action. Download Here. Sorry I could not Provide a better Hosting Service, Rapid Share is the only one I know of...
If by respawn in debug you mean you can save yourself after you die by quickly switching to debug, you can do that in the final. That's also in the final In fact I run into that a lot by accident, it's quite annoying sometimes.
Aw dammit... oh yes, I belive I metioned the Gravity changing in FBZ, but that's probably well known too...
This version is the first to allow you to break monitors from underneath, rather than Sonic 3's "hit underneath, knock the monitor down, and possibly get crushed" system.