Here's a kinda help:
It's illegal, because my friend downloaded AC09 for the Xbox 360
If you want, I can have a look through his downloaded files to see what there is
From what I know of , an Xbox 360 game disc can not be read by a PC in a manner that it would allow some changes to be made to its core files. The files that make an Xbox 360 game disc cant be read by a PC apart from the Audio & Video.TS files ( which is basically the video component on a disc used for playing a video in case someone pops up a Xbox 360 disc in a PC/PS3/Xbox1/DVD Player etc.) And even if we manage to make some changes to a Games disc ,its 100% illegal & it would require of people to use illegal methods of flashing which could even get their consoles Banned from the Xbox live .
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If there is any chance of Modding AC09 on Xbox 360 , it is to install the game to a HDD , transfer the game installation to a PC using a Xbox 360 Hard-Drive Transfer Kit
Then use Xplorer to browse through the contents of the HDD . And this IF ( a very big IF ) the games installation files can be read by the Big file editor , make changes to it . Re-transfer the modded file to the HDD Pray to the Mighty Lord & try to play the game.
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BTW, in my honest opinion .......... this should NOT work.