Kosta, if everything-that-there-is-or-can-be is known PERFECTLY, then there can be ZERO deviations from it.
There is zero deviation in the outcome of God's plan: God will save some, while other (the unrepentant) will perish. Nothing will change that. We have been told that the end is coming, the Kingdom of Heven is near. We were told in the scriputre how it will end and who will be there.
What we do with respect to God affects only our destinety and does not put in jeopardy God's plan, x! God made it possible with His sacrifice on the Cross for all men to be saved. But all men will not answer His call. That exercise of free will, which God permits, is our decision and the cosnequences of that decison are something we should be ready to bear. There is no free ride. There is no guarantee unless we persevere and live in repenetance.