Hehe this is the deal. First to answer you question.
Yes alcohol 120% should work fine. if you have the latest version.
And dump it totaly.
The 1.0 to 1.1 (I think) Was protection with SafeDisc 2.8 and 1.2 -> are protected with SafeDisc 2.9.
To your concern.
Like Eagle said, the Single player mission is not asking for CD-Key the Multi-Player dose.
Ubi-soft/ the dev. of the game did a bug when they released the Raven Shield. They forgott the CDkey thing.
So in 1.0 you can typ in any cd-key and run the game. And if you type so many letters as the origal cdkey has, it will dissaper the CD-key box.
in 1.1 they did the CD-key bugg, and there sulution was, to connect to there server, that could check if the cd-key was valid. Any way, the problem was, in LAN game, and if you play in private lan and have no internet connection it still wanna connect to UBI-soft server and check if you got a valid cd-key. And you can't lanch the game or the LAN server. THAT's what has been fixed. But every time you got internet connection and wanna play LAN games, you must have a valid CD-key.
So this only fix out, that if you don't have internet connection and wanna play multi player, you don't need a cd-key! by the way 1.31 LAN fix has been released...