Yes. They're all unique and you cannot use them more than once.
No, Mass Effect 2 has a completely different weapon system.
What code? If it's the game's actual registration code, and it is not working in Steam, you might have to contact their tech support to find the reason why not. If it's a DLC code, you need to login to your bioware social network account, that is where you redeem the codes.
There are 4 different codes regaurding the MASS AIR FLOW SENSOR. P0068 P0101 Po102 P0103
The registration code is usually found on the back of the game case, or the game's instruction manual. If you're looking for an exact code, it is illegal to use a different code than what game with your game CD (assuming you didn't just download it for free, which is just as illegal,) and WikiAnswers will not provide such a code.
Yes, the first Mass Effect replays carry into Mass Effect 2. The only things that don't carry over are the level ups, weapons, and armor. And that is because the combat system on Mass Effect 2 is completely different than the first.
There is no reason given by the makers of the game "Mass Effect" for Saren looking different than every other Turian. It is the general consensus, among "Mass Effect" enthusiasts, that the makers of the game just wanted him to stand from the others since he was a main character.
If he died in Mass Effect 1 then he is not in Mass Effect 2. If he survived Mass Effect 1 he shows up in Mass Effect 2 but he can not be killed.
Yes.
The effect of mass extinction is extinction, death of a mass
Yes, there will be a Mass effect 3. even if your Shepard died, there will be a mass effect 3.
mass effect 2 will be
BioWare, the developer of Mass Effect has confermed Mass Effect 2 to come out in 2010.