Yes, they definitely can.
When you first connect to live you go trough hv test and hypervisor to make sure your not on a hacked hand.
If the two profiles are different saves, they should indeed be able to work on a single profile.
No because when you do it will be a separate profile :D
yes you do the run the iso files(games)you have to have a modded xbox 360 unless you use the same programs microsoft does
You need a special xbox called a jtag that is a modded xbox designed to hack games although Microsoft can detect Jtag hacks so its a matter of time until your banned from xbox live.
no they do not if you put it on your file share=yes
no because on ps3 you need modded profile data
Yes you can. BUTTT the only way to do this is.... Step 1: Disconnect from xbox live or psn or whichever system you are on. Step 2: Delete the title update from your console. Step 3: You need a modded GPD. Step 4: Put the modded GPD into your profile. Step 5: Load OFFLINE zombies and enjoy the mods.
Call Microsoft.
I can insure you that you will not be caught by Microsoft and banned, Microsoft can not track your consol but can track your online account, but it don't matter since you got your Xbox 360 modded into the hardrive not on your online account so therefore Microsoft cant ban you and you are free to download any content online.
you can play ,but sooner or later youll be detected by microsoft and have your console banned !
If you attract to much attention to your profile they may do both.