Yet, all (except Judas)were saved men before Christ went to the Cross.
So, clearly their salvation was not based on what we have to believe to be saved, that Christ died for our sins and rose from the dead and is now at the right hand of the Father.
Their salvation was based on believing that Jesus was their Messiah and the Son of God (Mat.16:16)
They could only be saved as all before the cross could be saved, by faith in the unseen. IOW, faith that God the Father would not abandon them and he didn't he sent his Son to pay the price none could.
Hebrews 11:13 These all died in faith, not having received the promises, but having seen them afar off were assured of them, embraced them and confessed that they were strangers and pilgrims on the earth.
The surviving eleven Apostles did not understand the enormity of what Jesus did until the resurrected Jesus appeared to them. They had no special belief, or faith.
Mark 16:14-16 Later he appeared to the eleven as they sat at the table; and He rebuked their unbelief and hardness of heart, because they did not believe those who had seen Him after He had risen. And He said to them, "Go into all the world and preach the gospel to every creature. He who believes and is baptized will be saved; but he who does not believe will be condemned.
The Apostles were ordinary flawed people like us. Despite seeing all the miracles they didn't "get it" until after the resurrection. If they did truly understand they would have followed Jesus to the Cross and been on a Cross as well.
It seems this is the dividing line between dispensationalism and premillenialism. As a premill, I believe everyone from all ages has had the same criteria applied to them for justification. You are either righteous, or you have Faith in Jesus.