Okay. Got the patch and tested out some non-technical stuff to see what's changed. Here are my findings:

Jazz2.exe
I only found one change in the exe, one that fixes the local splitscreen multiplayer in the menu. Their lines were, besides Treasure Hunt, greyed out and unselectable. This patch however, still has those lines greyed out but they are selectable now.. Thus Co-Op, Battle, and CTF will now work locally. lol yippee. Strangely enough, CC99 had another similar bug which made Treasure Hunt greyed out and unselectable in the network/internet Host Server menu, and this patch doesn't even fix that. How sloppy.

Capture3 and Race1
These level files only have their Next Level setting changed. Capture3 will point to Capture1 instead of 4, and Race1 will point back to itself instead of Race2 as CC99 didn't came with any more Race levels. Strangely but nothing new, the default levels for hosting a server are CC99's exclusive MP levels, which are xmbattle1.j2l for Battle and XC-Frightni.j2l for CTF (that's non-exclusive user level Fright Night CTF).

Also, I don't know why but using this patch will break existing savefiles, resulting in either a glitched level (no bullets, etc) or an Access Violation Error. Probably due to memory locations being in a different place or something, I'm not too technical on that.

So that's it for this mystery patch! Basically, all it does is fixing local splitscreen multiplayer and preventing next level not found errors in 2 MP levels.