I'm not sure if this has been posted before, but during a browse I bumped into this:
There's nothing too different, just some rough character models, different angles for a few scenes, and an extended version of Miku vs Koji. There's also an orb meter when she's attacked and a blue flame effect on ghosts.
I hadn't seen this until today so it was a nice surprise!
Edit: just had a look at the uploader's other videos, there's a FF2 demo with what can only be described as Pigeon Mayu trying to take flight up some stairs at 6:56.