Only DarkBrotherhood quests will do impossible get other quests? (from NPCs i kill)

or have more quests? like civil war?

thanks

And LEFT EYE OF FALMER quest i cant get it when i get the item in PS3, with this update 1.5 will fix that?
and what i can do to get that quest? i dropped and get 100x and nothing =/

thanks

** What quests Will Make enable get others quest? **

I think most npc's that give quests are "essential" and can't be killed. Not sure if all are, though.