An unaltered build of the game (known as a "vanilla build" in the modding community) with files dating to November 1996 was publically released onto the internet in 2013. The vanilla (November build) was purchased by a fellow modding community member under the name "RMandel" and was leaked by others. This same build had previously been used by the IGAS Restoration modding team to create a heavily modified version of the game, known as the "Magic Zombie Door Build".
There are various interviews with Shinji Mikami and Hideki Kamiya describing the development process of the game and the struggles it went through.
Various indications on how far the development went can also be gathered the November build and the RE2 Final Trial Edition With 1.5 left overs and background files dating back to December 1996. With some of the lab rooms being still in wip state although 90% of the rooms have been completed.
No indication is included in any of the releases as to how far the sewers made it into development. They can be seen in early September 1996 looking completely different and another batch of few rooms working in progress during November. While Resident Evil 2 Preview (Trial) does not include backgrounds of the sewers (due to being overwritten by final files). It is unknown how the sewers would have looked like before being scrapped.