Sonic the Hedgehog 2 (Beta 4)

Sonic the Hedgehog 2 "Beta 4" of Sonic the Hedgehog 2 is a prototype version of the Genesis game. It was released during the February 23rd, 2008 proto release.

Beta 4, along with Betas 5-8 were not meant to be seen by the general public. Only days separate the build dates, all of which were created during the last two weeks of development.

The "beta 4" name originates from Sega themselves, having presumably succeeded a "beta 1", "2" and "3" in the days and weeks prior to beta 4's release. This naming scheme doesn't seem to include the earlier Nick Arcade and Simon Wai prototypes, likely due to being build months before REV00. But does seem to include the (slightly) earlier CENSOR prototype.