No. But you can on Black Ops. It's called Combat Training.
No
no
Yes.
cap of 9 vs 9 on multiplayer online
Special-Ops (2 players max) and Multiplayer (Up to 18 players in a single lobby)
the single player modern warfare is a campaign story, and the multiplayer has different game modes where you compete against other players and level up, but theres no story.
Well, Modern Warfare 1 on any console besides the Nintendo DS is multiplayer. But I believe you can system link play with the DS too.
Unfortunately no, you can't play multiplayer on Call of Duty Modern Warfare 1 or on Call of Duty Modern Warfare 2 on the same screen. But on Call of Duty Modern Warfare 3 and Call of Duty Modern Warfare Black Ops you can play multiplayer on the same screen. There is an new Call of Duty Black Ops 2 coming out soon though, so I expect that to also have that feature, since its newer.
You can, you just have to play Combat Training in multiplayer, you only fight computer players unless you allow others to join you.
Yes. Go to multiplayer, then to combat training. There you can pick the difficulty of the computer players and level up like on online play.
It's possible in the future
In "Call of Duty: Advanced Warfare," the AE4 is an energy-based assault rifle that can be unlocked by completing the "AE4" challenge. This requires players to reach level 28 in multiplayer. Additionally, players can acquire the AE4 through the "Havoc" DLC, which includes the weapon as part of its content. Once unlocked, it can be used in various game modes.