There are many interesting things in the prototypes of the Genesis Sonic the Hedgehog 2, most of which were sadly removed as development progressed. A total of ten prototypes, spanning almost the entire development cycle, have been discovered over the years. Most of them are very late in development as a result of being part of Sega's Quality Assurance BBS archives.
Nick Arcade Prototype A very early build still using many Sonic 1 assets. Named for being very similar, if not identical, to the build used on the game show Nick Arcade in 1992.
Simon Wai Prototype Considerably more fleshed out, but still clearly an early alpha. Named after the person who found it in 1998, Simon Wai.
August 21st, 1992 A very unstable alpha build. While many features still don't exist, this build is overall more complete than the previous prototype. Occasionally incorrectly known as the "Sonic 2 Alpha Build".
September 14th, 1992 A late alpha (or "pre-beta" as Sega called it) build featuring elements seen in some prerelease videos and pictures. Also known as the Gamesmaster prototype.
CENSOR Prototype The earliest known beta from around September 15-17, 1992. Named after the scene group that leaked it 12 days before the final game's release.
Beta 4 to Beta 8 Internal testing builds from September 18-24, 1992 that span the last week of development.
Knuckles in Sonic 2
To do: Prototypes beyond 0524 need to be properly documented, not just a link to Sonic Retro.
Include proper downloads for the prototypes.
Comparisons between the prototypes and the final build.
Almost all prototype versions borrow the header from Sonic the Hedgehog, with the only tweak being a "2" added for the titles. This was only changed to the final version's header in Beta 8.
Similarly, the Nick Arcade, Simon Wai and August 21st versions use Sonic 1's serial code, while all the post-August 21st builds have Sonic 2's serial code.
Tails Glitchiness
If Tails jumps and hits an enemy in just a few frames after Sonic dies, the score will continually increase until the fade-out. This happens because, while all Badniks are frozen and can't be destroyed just when Sonic dies, Tails can keep moving, get stuck in an enemy, and continuously gain points - a bug that (as seen in the video at right) awards 1,452,800 points and nearly 30 extra lives.
This bug is mostly present in the CENSOR build and later, but can be done in just about any prototype. It was fixed in the final by having Tails immediately go into his flying animation when Sonic dies, but can be reproduced through another bug.
When going up slopes with Tails' AI, if Tails does not successfully make it, its AI will walk back to a stop and then attempt to spindash up the slope. If Sonic dies during this time, Tails will continue performing this action until the Spin Dash is released, which then puts him into the flying animation described previously. If you take Player 2's controller to control Tails after Sonic dies and before Tails' scripted action finishes, you will have full control of Tails until the game fades to black, allowing this bug to occur when Tails jumps into an enemy.
