-The start-up sequence is missing the LucasArts logo, the "A Long time ago..." text, and the copyright disclaimer.

-The Rebel ship's engines are solid red during the intro.

-The Star Destroyers have different engine effects, featuring long blue flames.

-The Star Wars logo is missing a copyright mark.

-The intro states "Episode VI" instead of "Episode IV"...although I guess VI might be acceptable since the levels in this game are basically Return of the Jedi related.

-The intro text has not been completed yet.

-There are no demo sequences, and the alternate intro (featuring the A-Wings) isn't present.

-There are less sound effects and barely any music tracks, aside from a different sounding Star Wars main theme, which is used in the intro.

-32X mode isn't present.

-Some of the briefing screens have different text, and there are a few typos, such as "Super Star Destoryer".

-The wire frame graphics shown on the briefing screens are glitchy, and most of them don't display properly.

-There is no lightspeed sequence between each mission.

-The sequence showing your approach and entrance into the Super Star Destroyer goes on for longer.

-The Super Star Destroyer level has a different layout than the final version, most notably towards the end of it.

-The sequence showing the Super Star Destroyer blowing up isn't in place yet.

-The sequence showing your ship approaching the Death Star is missing.

-The Death Star surface is different, with more turbo lasers.

-The journey to the Death Star's reactor has a very different layout, and does not offer the two different routes that the final game has. You always have to fight the mobile missile launcher.

-The Death Star's reactor seems to take longer to kill and cannot be locked into with torpedoes.

-The ending isn't in place, and the game will reset once beaten.

-You can't score any points.

-Star Destroyers fire blue lasers.

-Sometimes when you die, your ship's engine trails will still be on the screen.

-You have to press X to fire torpedoes.

-Pausing the game and pressing A will move you onto the next level.

-You have infinite credits, although the game always states you have zero.

-Sometimes the progress bar will be white instead of red.

-When this proto boots up, a select screen appears. "Play level" lets you select any level you want, including some test ones, and some of the extra scenes -such as Admiral Ackbar's briefing -can be viewed. The ending scene showing Obi-Wan and Yoda is also something you can select. Several of the play level options don't work, sending you to a black screen, and the cinematic viewer doesn't work either.

-Beating a level or getting killed results in you being sent back to the select screen. The select screen also lets you select music, which features a lot of tunes that never made it into the final game! A sound effect option is also present, but it doesn't appear to work. The lasers make a completely different noise in this prototype.

-If you start a mission with enemy fighters in it, the game doesn't show how many you need to shoot down.

-Most of the differences with the previous proto apply to this one, such as the cut enemy in the Death Star's reactor.

-The copyright screen is now present.

-The second intro sequence with the A-Wing fighters has been added.

-The rankings screen has been added.

-Stat screens for the Rebel ships are now present, but they don't work properly.

-The intro text has been updated from when it was last seen, but still has several typos.

-32X mode has now been added.

-32X mode's ship selection screen is slightly different, as models for both ships are always present, and they spin around differently.

-During the first briefing scene with Ackbar in 32X mode, "Imperial March" plays, and continues to play when the first mission starts.

-In arcade mode, no music plays at all.

-Lots of sound effects and voice clips have been added.

-Rebel lasers now sound the same as they do in the final version.

-There are some issues with the briefing scenes, where text layers over other text.

-The Y-Wing is now present, and two player games are possible. However if the Y-Wing explodes, it has the explosion animation of the X-Wing.

-Star Destroyers now have the same engine effects as they do in the final version.

-At the continue screen you now only have two credits to beat the game with.

-The wire frame graphics now work properly, but the "destoryer" typo from the first proto is still present.

-There are some issues with garbage sprites appearing on the screen. TIE Fighters sometimes briefly display garbage sprites when flying past you.

-The Super Star Destroyer explosion scene has been added, but isn't fully complete -your ship isn't present, and the big ship isn't rocked by explosions before it disintegrates.

-When approaching the Death Star, the background doesn't have any stars in it.

-When you reach the Death Star's surface, after Darth Vader's TIE appears and leaves, no more TIE fighters appear, making it impossible to complete the level.

-If you die on the Super Star Destroyer or Death Star surface levels, your ship will fall through the floor if you die close enough to it.

-The level skip cheat doesn't work any more.

-The Lucasarts logo now appears with the SEGA logo, and a build date also appears in the bottom right corner.

-32X mode's ship selection screen now matches the final version.

-More music has been added, such as the theme that plays during each level.

-Different music is used at certain points. For example, when you beat the first level of arcade mode, the music that starts to play for the Super Star Destroyer level is what the final version uses for when you destroy the Death Star's reactor.

-If you repeatedly crash your ship into the floor or walls of the Super Star Destroyer, you can suddenly die instantly for no reason, even if you have shields left over.

-The counter showing you have many credits you have is glitchy, and doesn't display a figure.

-If you beat the Super Star Destroyer level, the game goes to a screen of stars and stops there.

-The build date no longer appears on the SEGA & Lucasarts logos screen.

-A new SEGA Interactive logo animation appears after the SEGA & Lucasarts logos.

-The intro text has been cleaned up, and is typo free.

-The "Super Star Destoryer" typo has been fixed.

-The graphical glitch with the credits counter has been fixed.

-The Super Star Destroyer explosion sequence has now been added, although some garbage sprites will appear on the screen for a few seconds.

-Stars have been added to the background when you approach the Death Star.

-If you die, the game goes to a blank screen.

-The SEGA Interactive logo has been removed.

-An orchestral version of the Star Wars main theme is now present.

-The continue screen now appears again.

-There are also prototypes for the 14th, 15th, 19th, 18th, 23rd, 29th and 30th September, along with more for the 3rd, 5th, 6th, 7th 8th and 9th of October. I haven't fully looked into all of these but they appear to be very similar/the same as the final version. The September 18th proto has the SEGA and Lucasarts logos separated, and now has music during the Ackbar briefing scene.

-There is also a prototype for the 6th of September which I haven't been able to get to work.