main game campaign missions are not available in co op .. also you have to play the single player game to a certain point before co op play is available
see http://www.co-optimus.com/article/12...co-op-faq.html
that page says the syringe mission is available .. but actually its not ...
the DLC for Valley of the yeti as well as escape from durgesh is also available in co op (both clients need to own the DLC for it to work )
as well as some custom maps provided the map maker enables it in their map
see this page about the custom maps features http://forums.ubi.com/showthread.php...ruary-1st-2015
and also
http://forums.ubi.com/showthread.php...-Editor-Update