Boosting.
No, only your online account. There are ways to glitch and prestige on Combat Training, but this does not affect your online account.
In Black Ops, you don't get an offline multiplayer account. It only shows your playercard from your online account. So the answer to your question is; you can't level up on your Black Ops splitscreen account because you don't get splitscreen accounts in Black Ops.
Yes
create one
no
No im afraid not sorry!!
no unfortunately not
no it will reset after you turn off or disconnect the guest
it is a mod, you have to mod your account to activate it.
you have to get to lvl 50 on your multiplayer account
No. You can only reset the level. If you die, you go back to your last check point. I wish you could.
The account does, but the Guest account doesn't get to save the points that they get.