At the very beginning of Act 1 Good Future, you can view a Sonic The Hedgehog TV, something that doesn't appear in the final. In both version's Bad Future there is an Eggman TV in the same position.

Also the platform Sonic is standing on is different.

For comparison, this is the same place in the final version. The floating block above Sonic stops Sonic from flying back to the baginning, and makes him drop onto the below Platform. In the 510 version Sonic goes straight through it.

In the 510 version of Sonic CD, this section has a whole section of detached conveyor belts, making it awkward to move through.

In the final version the below section has been moved up to make it have fluid movement.

In this large empty room, a platform moves side to side across the room to move Sonic across. It is also horribly discoloured.

In the final, the room has these small platforms moving in a circular clockwise direction, and fits much better into the room.

In room a swinging platform has been added with a conveyor belt on it. This platform does not exist in the final game at all.

In the final version, the platform has been taken away, the left set of sprites have been turned 90 degrees, the other set turning into a Monitor, and a spring added to reach the next destination.

In this very tall room, there are a set of jumping platforms which bounce up and down quite high from the floor. A set of clockwise turning platforms are also present.

In the final game, the platform style has changed dramatically, and the rotating platforms have been taken away. They were probably moved to the place mentioned a few images up.

In the 510 prototype version, these two crystals at the bottom of the floating platform do not exist. In the final, they come falling down onto Sonic if he's not careful.

Near the end of Act 1, this section of ground is left bare. In the final, both a diagonal spring and a set of spikes have been added.

For comparisons sake, here is what it looks like in the final.

In this quirky loop de loop, two platforms with palette issues have been jammed into the side of the wall. There is also meant to be a spring at the end of the first loop to push Sonic back down.

This is the final look for the same images above.

Here is another section where the swing was added inn the 510 version. It allowed you to reach the section without hurting yourself on the spikes.

Here is the final version. To reach the same area you would SPindash up the slope. The spikes have been removed, and the background has been made Pueple instead of black.

In the final game Sonic would fall into this tube and be shot out the bottom. In the 510 version it doesn't work yet.

This is the beginning of Act 2 on the prototype. In the final, the starting point is actually a level lower than this. It also puts you onto a collapsable piece of backdrop.

Here there is a yellow spring to the right of Sonic. In the final, the spring is hidden beneath the floor to the left of Sonic, and still activates when Sonic runs over it.

This is a picture from the final game. In the 510 version, the spikes and rocks to the left are not there, and were not replaced with anything.

This section from Act 2 is almost identical to the final, but in the prototype there are spikes after each swinging platform. In the final there is nothing there.

Like act 1, these zig-zagging platforms still exist, but in the final they have been taken out of the area. They can also crush Sonic for one reason or another.

In the prototype these spikes are stuck to the wall. In the final they have been taken off and replaced with a diagonal spring.

This weird section makes bounce through a walking underground area. However the springs aren't very strong, and only just make Sonic get to the edge. In the final Sonic is flung to another platform off screen.

Another appearance of the horribly miscoloured crumble platform. As soon as Sonic steps onto it it will make Sonic drop.

In the final version, the crumbling platform has been replaced with a floating block, which will drop after a second.

Unlike in Act 1, there is a tube warp which does work in Act 2. However Sonic clips through most of it on the way down.

When Sonic drops from the tube warp in Sonic CD 510 he'll drop onto these floating platforms. A rock also sits there aimlessly, and you cannot enter the upways tube because you cannot change the direction of the conveyor belts.

In the final the platforms are gone in place with a flat piece of land. A switch has been added so you can go up the tube, anda breakable column has been added to the far right.

These large brick walls are not present in the final version. They are also unbreakable by Sonic.

This little section is found in Act 3 of the game. Somebody added a whole lot of monitors, probably to just test out how everything worked. Oddly, they didn't add the other monitors only viewable in this version [Blue Ring, Super and Time]

When fighting the boss, a section of spikes sit at the left of the screen in impale Sonic. In this version, they just used smaller versions of normal spikes, with a plain, concrete backing.

In the final, large spikes are used to destroy Sonic. Sonic has also recoloured his machine to be Purple instead of grey.

When you go to destroy the capsule, a whole load of different flowers pop out. In the final another set of flowers comes out of it.

This is a comparison shot from the final. Also not that the entire capsule dissapears once broken, unlike the prototype. The sky is also blue instead of black, and of course new flowers pop up.