I generally like to work on side quests before the main quest. So far I've started a couple (Bane's and Zsasz's quests, for instance) that have objectives inside a big red "restricted area" on the map. I don't know what happens if I try to cross this boundary, as so far I haven't had reason to enter it.
Is it feasible to try to completely finish these side quests early in the story? Or should I wait until I have access to this "restricted area" later in the game? If I can't finish, is there any benefit to partially completing them now?