The first and most important rule of legitimate or popular government, that is to say, of government whose object is the good of the people, is therefore, as I have observed, to follow in everything the general will. But to follow this will it is necessary to know it, and above all to distinguish it from the particular will, beginning with one’s self: this distinction is always very difficult to make, and only the most sublime virtue can afford sufficient illumination for it.
Would you please help me to understand what the portion in boldface means?
And, to continue, is the following a question?
As, in order to will, it is necessary to be free, a difficulty no less great than the former arises
Rousseau calls on readers to distinguish—to recognize a difference between—the general will and the particular will: the Will of the People on the one hand and the will of particular individuals on the other.
He says that one must begin with oneself: that is, the most important and most difficult thing is distinguishing the general will from my own will, presumably because we all tend to think that what we want (especially in political matters) is what everybody wants (or ought to want).
He goes on to say that making this distinction requires an unusual degree of illumination or enlightenment; in fact, it is so difficult that only the most sublime virtue can provide sufficient illumination.
I do not address your second question here; it should be posted separately, with its context.