Sonic Heroes: The speculation on the old thread was that it used a different. Unfortunately, this is not the case. In fact, this build is slightly newer/more complete than the 10.8 build, but not as complete as the 11.18 build. Maybe 10.9 or 11.0? However, holding L + R and pressing UP, DOWN, LEFT, or RIGHT on the D-pad still bring the same debug commands as in the 10.8 proto. At this point, the "unlockables" such as super hard mode, 2P modes, and CG theater cutscenes are locked and need to be unlocked (except for the sound test for some reason and you can still see the thumbnails for the team's cutscenes in the CG Theater despite being locked). Casino Park, Ocean Palace, and Hang Castle all have their new music. Final Fortress's music (or Final Fortless as the great translation calls it in sound test) is still a WIP and sounds sort of trippy. Robot Carnival/Storm now has its music but sounds slightly different (maybe WIP?). Hang Castle inverted, Egg Emperor, Follow Me, Metal Madness/Overlord, sytem menus, and 2P mode are all missing their music. When selecting a team, they are in their final team pose and when you actually select a team, they have their animation. However, there are no voice clips when selected. There are probably still other details to point out, but there are the major ones I can pick up right off the bat.
Sonic Riders: Sorry to say, but there is not much to say. This build seems very finished. Possibly a review build? Can't tell until it's dumped, but there doesn't seem to be any differences.
Shadow the Hedgehog: Not a prototype, but a demo, and in Japanese. It features 3 stages (Westopolis, Glyphic Canyon, and Cryptic Castle) and a boss (Black Bull (the Westopolis fight)). You can't go past the goal ring in Westopolis, due to lack of ramp. Gylphic Canyon is pretty much the same as the final. Same for Black Bull. Cryptic Castle on the other hand ends much sooner in the stage (so Cheese is in a different spot if you are doing the hero mission. However, the results screen takes place at the alter with all the chao. There are still 5 lanterns to light for the dark mission, but I haven't tried that yet, so I don't know how the stage ending sooner affects that mission). As per most demos, completing a stage gives you a coming soon screen and then takes you back to the title screen.