On the title, sound test is unlocked from the start. Doomsday still has whistle sound effect for no reason. Beginning section of Doomsday is hell of long but my memory of it in the final is fuzzy. In the special stage: "WOOP" noise when you lose is gone. Item bubbles fall DOWNWARDS. Looks like the bottom border rises faster.
From 2 seconds with this proto I've already discerned that Hyper Sonic, while implemented, has a constant circle of stars around him, though not in the same style as the Invincibility powerup. The intro to Mushroom Hill does not appear to have been implemented yet; Sonic and Tails begin standing in mid-air and simply fall to the ground. The Hidden Palace scene when you enter the Special Ring at the beginning of the stage plays Death Egg Act 2 music, unlike the zone itself. Sonic does not fall under the sand and pop back out in the intro to Sandopolis; he merely falls from the sky and lands on the ground normally. Lava Reef 2 does not have the screen locked at the start of the level as in the final when accessed from level select. The lava is not cooled off at the start, but the zone uses the same blue palette as the final at this stage in development. Lava Reef 3 (Sonic's boss) uses the Lava Reef 2 music as opposed to the Boss Theme used in the final. Hidden Palace still has Sky Sanctuary Music - the row of monitors near the top of the level still contains an S monitor instead of Speed Shoes like the final, but the row of monitors to the right is now two Super Rings and a 1-up like in the final (as opposed to Sonic 3C 408's three 1-ups). There is still a Fire Shield next to the teleporter that takes you up to Knuckles, instead of the Super Ring that's there in the final. Knuckles' boss still plays the Sonic 3 miniboss theme. The scenes after defeating Knuckles occur pretty much exactly as they do in Sonic 3C's 517 beta, but as in the final Robotnik no longer flashes when hit by Knuckles. The Doomsday Zone automatically starts you as Hyper Sonic when accessed via level select, unlike the final where you are Super Sonic if accessed in this way. The zone's background also has a different, greyer pallette, and the zone scrolls a LOT more slowly to begin with - you can speed up the scrolling by holding right to gradually accelerate it, but hitting an asteroid will slow it down again. No SFX plays when breaking the asteroids. When the boss reappears after its' blue armour is destroyed the 'badnik popped' sound effect plays instead of the sound played in the final. XD Hidden Palace Zone is accessible from the level select - as are all the Sonic 3 zones, bizarrely enough, considering this is a 3B proto not 3C. Knuckles' theme tune is the version from Sonic 3. The Sonic 3 Miniboss music is also still in the Sound Test and used for all Act 1 bosses and the Knuckles Hidden Palace boss. The invincibility / Super theme is from Sonic 3, however the title screen theme and 'game complete' jingle are both the versions from the final Sonic & Knuckles. I'm off to explore this a bit more - will update this post if no-one posts before I find new stuff; if not, will post a new post with more info. =P
from playing for a few I noticed a few things, which were mentioned Stars around Hyper Sonic different, they are horizontal while running. in the machine bonus stage, the bubble shield didn't override my lighting shield beat doomsday (at least with Debug) the credits don't show Eggmech's Master Emerald Beat hurts Hyper Sonic Beat Deathegg Act 2's boss (casing Eggman) he leaves the screen, and after beating him, screen turns white and music keeps playing
Also of note; although the 'game complete' jingle is the Sonic & Knuckles version, it's actually an earlier version of the tune. It sounds pretty much identical up to the final note, but the timing for that note is very different and there's no background jingle echoing off afterwards like in the final version. Come to think of it, is that jingle even used in the final S&K? It's sound #32 in the Sound Test, for anyone who doesn't know what I'm talking about.
Did anyone else notice that Sonic moves noticeably faster then Tails at top speed? Super and I found this out when messing around in Lava Reef Act 2 where there is a large section where you can run backwards on lava.
Slot machine bonus round - rediculously different object (bumber, changing block, left/right direction changer, etc) layout
S monitor makes Sonic Hyper, not Super. The sparkling is way different and cooler than in the final too! You can not control Tails for all of Hidden Palace after Knuckles is defeated.
No special SFX or boss music for Lava Reef 'Act 3' (The lava thing) and the sinking maga waterfall platforms have a weird looking thing under them, like a different animation. The platforms which crumble are acting strangely. After beating the boss, the platforms retain their 'bright' colors. The one you're standing on floats to the right (???) and stops when it reaches another one. Right after: Tails is not beamed up by first teleporter in Hidden Palace Zone. Weird version of Death Egg rising sound effect in Sky Sanctuary zone. Eggrobos make black smoke when defeated. Death Egg engine sound in act 1 goes to a lower pitch before ultimately cutting out. Metal Sonic will attack you over again if you use a star post and fall down to one of his bosses in Sky Sanctuary even if you've already defeated him. 'Rising up' sound after defeating Act 2 of Death Egg's boss different pitch. Jumping on upside-down track thingy in Act 2 can reveal a black box which covers over some of it.
This applys to Knuckles too, when he hits the wall the screen shakes like Hyper Knuckles does in the final S3&K, the sound effect doesn't play though but it does destroy the on screen enemies.
In the slot machine bonus stage, the background is also in an early stage. It's completely static - the little objects don't rotate and nothing scrolls.
Lock on wasn't implemented in this build, it seems. This could very well be Sonic 3C instead of B, but I have to check more carefully.
Game freezes at the moment. Conditions: Debug Enabled, S Box for Super Mode, Hydrocity Act 1 You cant die this way.
If I recall correctly, that jingle in the final is at the end of the credits music, Sky Sanctuary fades into it. I don't think it was ever used standing alone, and the ending does indeed end slightly differently, much more abrupt. Going completely from memory there since it's 6am, not slept. Might be wrong, 99.9% sure I'm not.
Sometimes, if you leave the water, your acceleration/decceleration values are unchanged from when you were submerged.
Lockon is partially implemented in this build, in the way that it uses the appended Sonic 3 ROM for data. I tried removing the Sonic 3 ROM to see if there was a different title screen for S+K alone, but it's not implemented yet (fails to boot).
I was about to reply myself, but yeah, I was completely wrong. Lockon IS indeed implemented in this build, to a certain degree. First of, as I expected, there are NO references to the sonic 1 header. The blue spheres game is missing, but the jump to the s2k chip is there. Any other header not matching with a revision of sonic 2 will run the same code as if was attached to s3.
