Okay, I have a list of stages from Sonic 4 Episode 1. I don't know if it's complete or not, but here it is:

STAGE LIST:

Splash Hill Zone Acts 1-3
Casino Street Acts 1-3
Lost Labyrinth Zone Acts 1-3
Mad Gear Zone Acts 1-3
Special Stages

Click the stages with a link for a picture. Sorry about the bad images, they're all I could find. I'll update it when I can.
This is not a guess. I got the Sonic 4 OST and these are the stages. Here's more proof. If you still don't believe me wait for the release.

Here's a list of badniks. This one I'm pretty sure isn't complete:

BADNIK LIST:

Crabmeat
Motobug
Newtron
Bubbles
Chopper
Buzzer
Jaws

If you don't know much about them visit the Sonic 4 Website and go under the section "Badniks," or click the individual badnik's link.

The entire game was leaked some time ago. I don't know if you knew that or not. It caused a massive ruckus on Sonic Retro. So bad that they closed the entire thread, and had TWO Shark weeks. It wasn't a pretty site.

I didn't know that. I never saw that thread, though. But anyways, this is a little list of info, though. I just put it up in case it would be nice to have.