Unfortunately, Onslaught was canceled due to work on Battlefield 3, as was Battlefield 1943 for PC.
no
No. Would be too easy to boost if they did.
Onslaught mode is available on the Xbox Live Market Place for 400 Microsoft points. There is also a in-game store that will take you right to where you can purchase the game add-on.
Yes and no, BC2 does a have a single player mode and a multiplayer mode
Yep
Depends what you mean. There is a campaign mode and a Multiplayer so no its not?
They're at your base when you respawn. You have to be in rush mode though.
It has a Campaign mode (Singleplayer) and Multiplayer.
yes there is
Battlefield 3 does have Co-op mode, you can also unlock weapons for use in Multiplayer from playing Co-op.
Yes there is a multiplayer mode for the game that was released for the PS3 on June 4 2010. see related link
Nope, sorry there is no spectator mode in battlefield 3.