When was the plan of salvation pre-planned?
The plan of salvation was pre-planned before anything was ever created. God determined that He would create man, that man would sin and need a Savior and Redeemer, and that Christ would die for our sins according to the Scriptures. This purpose was set in motion before creation.
Les explains that this was all pre-planned before anything was ever created. God would create man, and man would sin and find himself in need of a Savior, of a Redeemer. God set everything in motion, brought about Christ in His earthly ministry, brought about His crucifixion, and raised Him from the dead, and brought Him back into the very portals of heaven. From there He revealed these things that Paul calls the Secrets, or the Mysteries, and the very core of that is the Gospel, that Christ died for our sins.