Red Mountain has many locations where the camera likes to go to undesirable places (due to its camera files, at least for Sonic, being extremely old and expecting a different version of the list) and make playing the level extremely hard for the player. This is also the stage used for Gamma's and Knuckles' demos.
Sonic's spawn is in midair above his regular starting point, much like in Emerald Coast.
There are three Kikis on the crates at the start. In the final, one of these Kikis has been moved to the ground on the left:
Proto
Final
A "?" ring box on a platform that can be seen taking the first rocket was replaced by a floating 10 ring box.
Dropping down from the first hanging ladder is an area with a circle of 7 rings, a Sol, and a rocket. In the final, the circle of rings was changed into two squares of 4 rings.
A line of 5 rings after the hanging ladder was reduced to a line of 3.
Just before the first checkpoint is a crate with two Kikis and a line of 5 rings behind them. In the final, the only thing that remains is the line of rings, which has been reduced to 3 rings.
The first checkpoint has been moved slightly forward in in the final.
There is no Tikal hint ball at the second rocket.
The large tower that the player can reach with the second rocket does not having a spring.
There is a Kiki placed next to a Sol after the small tunnel that is missing in the final.
The ground after the tunnel has strange properties that make Sonic accelerate faster.
Under the collapsing platform near the second checkpoint area is an extra spring.
The bridge at the second checkpoint takes on a red appearance:
Proto
Final
Across the bridge, two spike balls are missing and there are fences to the right, discouraging the player from going up to the top.
The top of the mountain after the second checkpoint is empty. In the final, there are item boxes and a spring.
There is no item box on the zipline.
The area with the first zipline start has an extra Sol and the platforms at the back of the mountain are arranged slightly differently.
There are Spinners in the area after the zipline/third checkpoint that aren't in the final.
There is an item box missing after the spring.
The object layout on the wall after the collapsing platforms includes a spring, two Spinners and three small platforms. In the final, the Spinners are changed to form a line to the platforms and the spring is missing. The platforms have also been made larger and a line of 3 rings has disappeared:
Proto
Final
The area around the next rocket has more crates on the left side with an extra Kiki and a 10 ring box. In the final, this has been reduced to one crate with a single Kiki:
Proto
Final
Even closer to the rocket are two crates and a lava geyser. In the final, this is replaced by a skull flamethrower and a life box.
The part before the hanging here has a Sol on the left side. In the final, there is nothing but a 10 ring box on the right side.
There is no Tikal hint ball after the hanging ladders.
There is no "?" item box after the set of three springs after crossing the second bridge
A line of rings on the path to the last rocket is missing.
A life box, Kiki, rings and the last checkpoint are missing.
It's possible to walk on the sides of the top of the mountain. In the final, this is blocked by an invisible wall.
The third hanging ladder is missing, with a small part where Sonic must walk across a rock in the wall being used instead.
There are only two rings in the hanging ladder section.
There are 5 rings and two fire-breathing skulls on the other side of the lava pool. In the final, there is a fence and 3 rings.
There are no objects surrounding the last zipline. In the final, there is a set of Spinners and an item box.
The transition to Act 2 covers a much larger area. Sonic will go to Act 2 as soon as the second zipline ends, instead of when he jumps into the hole nearby.
Act 2 (Sonic)
If the player enters Act 2 from Act 1, the lighting will still be absent. To get the lighting to show up, the player either needs to enter from the level select menu directly or reload the level via dying/restarting.
The camera notably messes up in the first hallway and goes to the start of the stage, making it very difficult to play normally.
A Sol and a line of rings are missing in the path split at the start of the stage.
The giant spiders are untextured.
There is a missing Shield box just after the first spring.
There is an extra set of crates and a Kiki just after the first homing attack line of Spinners.
Rings over the platform after this are absent.
There is a 1-Up box on a rock to the left in the part where Sonic runs across a slope.
There is an extra spring after the second checkpoint in the collapsing rocks section.
There is no Shield box, rings, or Spinners in the collapsing rocks section.
There is a spring at the end of the collapsing rocks section. However, usually that spot is covered in lava, so the player never sees it. It's very easy to accidentally homing attack this spring and get hurt by the lava.
In the part where Sonic runs along the second slope after this, there is an odd line of 9 rings. In the final, this has been replaced by a line of 4 rings.
After the slope there is a part with multiple circles of rings and two Kikis on crates. In the final, this was reduced to two Sols:
Proto
Final
A 10 ring box that is behind the crates was moved to the right slightly and turned into a "?" ring box in the final.
The section with the prison cells has an extra Sol.
At the part with the collapsing platforms, there are two Spinners not present in the final.
The line of rings near the collapsing platforms is missing too.
The line of rings on the collapsing platforms has been reduced from 5 rings to 3.
There is a set of crates humorously breathing fire. In the final, it was replaced with a falling spike ball:
Proto
Final
A line of rings at the three dash panels on the small ramp at the top of the stage are further back than the final, making them intersect with the panels.
A floating 10 ring box after the dash panels is missing.
Two "?" ring boxes are missing at another 10 ring box location nearby.
The fire-breathing skulls in the last hall are in different positions. They're all on the ground in an alternating pattern, as opposed to the final where two are slightly elevated and the skulls face each other:
Proto
Final
Act 2 (Gamma)
The first wall in Gamma's stage has 3 targets. In the final, there's 4.
Kikis on the walls near Gamma's starting point are missing.
The first fork has fences and fire traps that aren't present in the final version:
Proto
Final
A shield box is missing after the fork area.
The second wall has 2 targets. In the final, there's 3.
A rock near the first spring is made smaller in the final.
Item boxes behind the Spinners at the first spring are missing.
Item boxes are missing in front of the platform after the checkpoint.
Three Spinners on the second lava platform were changed to a wall in the final.
The checkpoint at the area where Gamma enters a hole in the floor has been moved before the hole rather than after it. There is also a Tikal hint ball:
Proto
Final
There is another Tikal hint ball after the small tunnel before the boss.
E-104 does not get knockback or any effects when hit.
E-104 does not turn into an animal when defeated.
E-series boss music does not play during E-104's fight.
Tikal's hints read:
Japanese
Translated
どこかに隠れた通路があるはず。 探してみて。
There should be a hidden passageway somewhere. Try looking for it.
ダイナマイトを壊せば 先に進めるわよ
If you destroy the dynamite you can continue on ahead.
Act 3
Act 3 seems to be using the version of the level from the TGS build of the game. The tutorial for Knuckles is present and there are many more Tikal hint balls present than in the final version. The Master Emerald shards are always in the same places - in front of the starting point, underground at the area Sonic lands at after using the jump panels, and near the falling spike ball in the area just after Sonic's first zipline.
The TGS tutorial.
The first shard.
The second shard (buried).
The third shard.
Knuckles' starting area only has 3 rings. In the final, there are 6 rings and a Tikal hint ball.
There is a floating line of four rings in front of Knuckles' starting point. In the final, this is a 10 ring item box.
Tikal hint balls are present near the shard at the starting point. One is next to the shard, one is on the bridge, and the other is on the other side of it. The third one was moved to Speed Highway in the final.
A line of rings on the path to the rocket at the bottom of the mountain are missing in the final.
The switch puzzle for the rocket from Sonic's level is used in Knuckles' level too. In the final, Knuckles' rocket is already activated and the switch has been replaced with a square of 4 rings.
Knuckles' restart position is at the same place as the first Emerald shard. The final uses his original starting point.
A 10 ring item box and an invincibility box are missing on the side of the mountain below the area with the rocket.
At the top of the mountain are three Tikal hint balls. In the final, one was removed and two are in different locations.
The zipline platform is empty. In the final, there is a Kiki and a circle of rings.
At the line of Spinners near the starting point, there is a Tikal hint ball that is absent in the final.
The line of 4 Spinners was replaced by a line of 3 in the final.
A 10 ring box opposite the leaning platforms is missing.
Underneath the collapsing platform after the first zipline section is an extra fire-breathing skull.
Another extra Tikal ball after the collapsing platforms near the jump panel section. This one (where Tikal talks about buried Emerald shards) was moved to the starting point in the final.
A Spinner was moved from over a pit to near the collapsing platform area in the final. The number of them was also reduced from 3 to 1.
A Kiki was replaced with a Sol nearby.
On the top of a mountain behind the starting position is another extra Tikal hint ball.
To the right of the starting point is a small, but tall mountain. On top of it are two spike balls and a Tikal hint ball. In the final, there are 3 spike balls in a triangular formation and a 10 ring box nearby.
Tikal's hints read:
Japanese
Translated
困った時は私を探してみて。
If you're confused, try to look for me.
Ｌ.Ｒボタンで カメラをまわすことができるわよ
You can rotate the camera with the L and R buttons.
