Knuckles in Sonic 2 prototype 0612 for the Sega Mega Drive/Genesis was released by drx during the February 23rd, 2008 proto release.
This prototype, along with every available build after the 0524 prototype, is a dump of the Sonic & Knuckles UPMEM chip. In order for this build to be playable, it must be attached to the beginning of a Sonic 2 ROM. Merging these two ROMs emulates the use of Lock-On Technology. The Knuckles in Sonic 2 0524 prototype is the only prototype released as a working stand-alone build.
- Level Select is not enabled by default. The cheat code is the same as the final version.
Sonic Retro discussion thread