God's people are elect from eternity but they are absolutely not justified from eternity.
Isaiah 12:1. 'And on that day you will say: " O LORD, I will praise You; though You were angry with me, Your anger is turned away and You comfort me.' 'That day' is the day of Christ (Isaiah 11:1, 10) but how can God be angry with those He has declared righteous?
Ephesians 2:3. '...We.....were by nature children of wrath.' How can we have been if we were declared righteous in eternity?
Titus 3:3-5. 'For we ourselves were also once foolish, disobedient, deceived, serving various lusts and pleasures, living in malice and envy, hateful and hating one another. But when the kindness and the love of God our Saviour towards man appeared, not by works of righteousness which we have done, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit whom He poured out upon us abundantly through Jesus Christ our Saviour, that having been justified by His grace, we should become heirs according to the hope of eternal life.' The kindness and love of God our Saviour 'appeared' - they were not from eternity - with Jesus Christ.
Justification is by grace, but it is also by faith (Romans 5:1.), and we did not believe in eternity, but when we heard the Gospel and God the Holy Spirit graciously applied it to our hearts.