A. Yes it is.
B. The preamble describes what the rest of the document is for! You're saying that the "introduction" to the Constitution has nothing to do with what it's about?
Which is another reason I suggested you take the free online course offered at Hillsdale College on our Constitution. You and all the other far left folks demand that the Constitution mean what you want it to mean and not what it says. That's typical of the far left, something of which you are very familiar.