Hello Athanasias,
Just because the saints were there at creation, 'shouting for joy', does not mean predestination. It means that God, and those eternally Begotten of God, meaning the saints, live outside of physical time. Those born of God are omni-present with God and can experience the whole of physical time as God can.
People have free will on earth to choose whether or not they will love God through obeying God. At the end of time all people are judged by Jesus as to how they conducted themselves in life. Those who have done as Jesus commands them to do in life, are judged by Jesus into spiritual life through His blood. The saints then live in omni-presence to the whole of physical time. Those people eternally begotten of God at the end of physical time, now resurrect to sing a hymn of praise as God brings creation into existence. Some people confuse this to be predestination. It is not. It is the awesome Power of God.
Creation
NAB JOB 38:7
Where were you when I founded the earth? Tell me, if you have understanding. Who streched out the measuring line for it? Into what were its pedestals sunk, and who laid the cornerstone, While the morning stars sang in chorus and all the sons of God shouted for joy?
NAB DEU 32:8
When the Most High assigned the nations their heritage, when he parceled out the descendants of Adam, He set up the boundaries of the peoples after the number of the sons of God; While the LORD’S own portion was Jacob,His hereditary share was Israel.
NAB WIS 5:5
See how he is accounted among
the sons of God; how his lot is with the saints!