To answer in Short : Yes,

You cn Create any mission (SP or MP) in The OFP Game, just like in Arma, ArmA II and Arma III.
Sadly though, OFP MP gaming is very Limited compared to ArmA2 and ArmA3.
Such as you have to have all player's active in the Said MP you are playing, If anyone has been Dis-connected from the game, they would have to wait till the game finished, or restart the MP mission, and lose all that you have done up to that point.