Can a mod from 360rev mess up a multiplayer game even if the mod is for something else? Like the MW3 mod or Halo Reach mod for invinciblity?
Not quite sure what you're asking. Do you mean that if you mod the single player campaign of game, will it mess up your multiplayer?
I think that is what he is asking and from my experience the answer is NO i have never had any problems on multiplayer after using modded SP files
No, mod tools edit certain areas of code where the stats are hidden.. it does nothing else anywhere else. your multiplayer is 100% safe.