I happen to still own my original release JJ2 CD with version 1.20 from 1998, and despite being pretty badly scratched it happily still works! This green CD with the grey JJ2 logo is the UK release which was distributed by a company called Black Friar. I've seen multiple different CDs for JJ2 online but to my knowledge this design with the tagline "He's At It Again!" was exclusive to this UK release.





The number 2 on this title card was pink for some reason.





As for the game itself, the most notable difference in the menus is that the old green logo design from the beta versions is still used, and that the menu has a bluish background rather than being mono-purple.





Unlike later releases, 1.20 did not come included with any custom levels.





In terms of gameplay, it's not significantly different from later versions. The most notable differences that I noticed as follows:

• Carrots can be eaten even when at full health. You don't get any extra health beyond the maximum, but you still get points and the temporary invincibility.
• You can also collect ammo even when you have the maximum, and you won't get any additional ammo for doing so.
• Airboards can be used underwater, as seen below. They have pretty glitchy behavior, with frames often skipping back and forth between airboard and swimming animations. You can even buttstomp underwater with them which is bizarre, since you can still see the airboard animation while doing this!
• Fire Shield bullets work underwater, also see below.
• No Capture 4 (Chemical Warfare).
• It's possible to get stuck in masked tiles with One Way events by buttstomping on them. With very thin masks such as the "Tower Oaks" sign in the Colonial levels, it is actually possible to completely phase through them!

There's also allegedly a whole bunch of improvements to the multiplayer and online netcode in later patches, but I can't assess those because of the lack of 1.20 compatible servers.



So there you have it! I hope that answers all your questions.