As for demonstrations, what you said is incorrect. There is no obligation for the prefecture to approve your request before you go on a demo. There is indeed an obligation to declare it but unless it's explicitly forbidden you are go. It used to be, not so long ago that undeclared demos were legal and i believe it was only under nazi occupation that they weren't. Sarkozy changed that to repress young people hanging out in public spaces by making 3 people or more hanging out together illegal.
It's important to understand that outlawing demonstrations in France (along with other obvious signs of growing fascism) are a rather recent phenomenon. Except for workers/ecologist or pro-Gaza demonstrations repressed in the past decade, the last forbidden demonstrations in France date from the 60s (in support of Algerian independence).
Still, they'll never stop our "manif sauvage" :)