How much did the Twelve know when Acts 2 happened?

At Acts 2, the Twelve knew not much more than that Christ had come and fulfilled all the Old Testament promises. They did not yet understand the Gospel Paul later defines in 1 Corinthians 15:1–4, that Christ died for our sins according to the Scriptures.

Les explains that the apostles whose doctrine the believers continued steadfastly in were the Twelve. When Acts 2 happened, these twelve men knew not much more than that Christ had come and fulfilled all the Old Testament promises. Les points out there was nothing yet indicating they believed what is now called the Gospel—the message Paul later received in 1 Corinthians 15:1–4 that Christ died for our sins according to the Scriptures. Instead, Peter’s message was “You killed Him,” a total difference. Les notes this was a furtherance of John the Baptist’s message of repentance and baptism, now based on the finished work of the cross, but not yet the revelation of the Gospel of grace.

Who were the apostles in Acts 2:42 and how much did they know?

The apostles in Acts 2:42 were the twelve. Their knowledge was limited: they knew not much more than that Christ had come and had fulfilled all the Old Testament promises. The passage gives no indication they yet believed the Gospel Paul later defines as Christ died for our sins according to the Scriptures.