This is the Resident Evil's unreleased version for the GBC
In 1998, the McGovern brothers decided to leave Acclaim where they worked and created their own company called "HotGen".
To make a dynamic entry into the videogame industry, they decided, among other things, to fit PSONE's Resident Evil into GBC's cartridges and bring it as close as possible to its original version. In May 1999, they intended to present it on E3 and circulate it on Christmas of the same year, but Capcom was unable to anticipate the holidays.
The time has passed and the game never released, with Capcom saying the game would not make the players happy. Later, Capcom created their own version of the DS game.
Capcom's DS Release
Over time, at assemblergames forum, some user decided to create a funding so they can collect $2000 and buy the original cartridge from its owner.
The money was collected and the game was bought. However, it was not 100% playable, as in some areas there was no access.
Thanks to the work of forum users though, the game is almost 100% playable and you can find it with a simple search.
See the below videos, as well as the pictures following.