You can't!
No you can't be a venom in Spiderman 3 xbox 360.
to unlock venom on spider-man 3 you have to get 100 of the purple things you will here m m m m m if it get louder that means your there if it get lower that means you are not getting to it (It Will...
yes
To get the black Spiderman suit you have to beat the grand finale mission
no their is no cheats for spiderman 3 o0nly games with cheats on xbox360 are guitar hero 3 and gta5 but they dont help u to get achievements.