PS3 & MW3 Unlock?

I everyone, this is my first post & in the world of games, a noob. What i need help with all is...

I have MW3 and finished the game several years ago, and rarely play, but over the weekend i had a mate over and we were just playing multiplayer (offline, don't play online ever). And got annoyed that although i have finished the game, i was unable to select the "cooler" weapons and such (when setting up user classes), and although he has a profile set up, my rank was better so he had even worst weapons than i.

Both the game and the system are genuine articles, and to this point not been touched. My console has not been "updated" with a PUP file in 5 years. Is there a way to unlock all weapons, ranks, etc? I have looked around myself and anything i can find like ("Call of Duty Modern Warfare 3 Advanced Unlocker") seems is for unlocking PC versions and not consoles. As i don't play online i have no problems with jail breaking it, if that will fix my prob.

Any help, suggestions greatly appreciated!