Is there victory of Satan

I don't think it is a victory. God is never defeated. The Fall of Adam and Eve is really directed at the two mortals rather than Satan. Milton's stated purpose is "to justify the ways of God to man," and he does so by placing responsibility for the fall squarely on the shoulders of the first human pair. They are cast out of Eden because their banishment is necessary to fulfil the demands of divine justice. Their punishment is just, because God placed only one condition upon them and they failed to fulfil it, in spite of the fact that God gave them the means to do so.