Co-op playability of game and expansions?

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Forgive the newb question, but it's really hard to find a conclusive answer on Google that doesn't raise other questions.
Looks like a fun game to play with my friend but I'd like to know more about what I'd be getting.

For the following games...
MoW,
MoW:Assault Squad,
MoW:Red Tide,
MoW: Vietnam,
...which are playable as coop to finish the same missions as in the single-player mode? Via LAN or internet or both?

For the original MoW, Co-optimus website says that you need a patch to play the actual campaign but that the single missions are available. Huh? What is the nature of such single missions compared to their campaign variant? If this question is applicable to the other expansions, then I'd like to know for those too.

Thanks.