Sonic Adventure 2 Preview V1.001 2001/03/18 (Subject) dreamcast
It is not unpublished but remains nonetheless interesting.
This Beta didn't quite show what the game was going to look like. We could therefore get an idea while keeping the surprise on the final product.
I see it being distributed mainly to journalists.
You can download it below:
Some prototypes related to sonic:
To read an article on Sonic's 15th anniversary, head here.