Don't forget Sega accidentally uploaded the Steam beta for Episode II as well! It's pretty funny how in both cases, these so-called "early betas" were pretty much identical to the final games outside of a few elements.
Yup, Episode 2 leaked a few days early by accident. The Episode 1 betas were definitely more revealing though, as they were still based off their mobile counterparts before everyone demanded blood and they made up two new levels for the console version. Episode 2's beta was more akin to one of the later Sonic 2 beta's in that it was basically the final game, but a few more bugs and some missing textures. Other than that though it was the final game.
The Episode II leak happened a few weeks (April 21) before the final game (May 15), not a few days. I agree with the rest of your post though.
I've always wondered if someone inside Sega was unhappy with Sonic 4 EP1 and leaked it in the hope that it would create a negative reaction in order to convince Sega to refine it. It's just odd how much it was leaked.
That's what most beta-stage software is; the content intended to be in the final is locked down and the bug hunt / polishing begins. Stuff like the Sonic 2 Simon Wai Beta is more like an alpha, but the name stuck.
Yeah, but by the way they referred to those games as "early beta", you'd expect the content in there, but the game being very lacking in polish and having tons of bugs. Episode I's beta arguably has almsot no bugs to it, and the worst Episode II had to deal with was some unfinished textures in the first zone.
I'm no software engineer, but building it off the Sonic Rush engine meant it probably just "werked" from the get-go.
Nah IIRC it leaked through the Xbox Developer Preview Program, which tons of people had access to. What takes the cake is the Wiiware beta that leaked because SEGA of Japan straight-up put the wrong build up for sale.
They also replaced Lost Labyrinth Act 2. It was originally this godawful, tilt-controlled mine cart stage, but was changed to a slow platforming level where you had to light up hallways with a torch to see where you were going.
I have a small announcement, You know the Casino Street Act 2 that's exclusive to mobile? Well, The very same stage is in the wiiware version. And since the wii uses the Brseq format I was able to get a midi of the beta Casino Street Act 2 that I'll upload here to complete the Sonic 4 midi collection, I also managed to rip every single texture in both games if you want them for some reason, Just give me a shout! I'm here to help! Here's the midi for Casino Street Act 2 beta. https://drive.google.com/file/d/0B2NJ7TQspBmsSzlfQzNFWkVYQ0k/view?usp=sharing