The following supposed differences are just made-up. Doesn't take much common sense to see their error in that two-gospel cult.
Here are differences in preaching between the twelve apostles and the apostle Paul:
1) The name of Jesus
The twelve preached whosoever believed in the name of Jesus was saved (John 1:12 John 3:16-18 John 20:31 Acts 10:43). There was no mention of reconciliation by the cross (Colossians 1:20), and in fact the understanding of the death and resurrection was hid from the twelve (Luke 18:34).
Of course the first Apostles didn't understand about Christ's crucifixion and resurrection until... they SAW it. Then when He appeared to them after His resurrection, they were certain. So trying to make a difference between how Salvation was preached prior to Christ's death and resurrection vs. afterwards is an unrealistic comparison. It doesn't prove the existence to 2 different gospels. Instead, it proves the existence of the ONE Gospel, which was prophesied even by the OT prophets, for David was given to prophesy of Christ's crucifixion even about thousand years before it happened (Psalms 22). The OT proclaimed, the NT witnessed and confirmed, ALL the 'same' Gospel of Jesus Christ. Christ crucified is what Apostle Paul preached too.
Paul preached salvation in the name of Jesus (1 Corinthians 1:2 1 Corinthians 6:11 Ephesians 5:20) and by the cross (1 Corinthians 1:18 Colossians 1:20 Galatians 6:14 Ephesians 2:16).
Jesus had already died and resurrected when Paul did that preaching, so no brainer.
2) Baptism
The twelve preached salvation upon baptism (Acts 2:38 Mark 16:16)
Paul was not sent to baptize (1 Corinthians 1:17)
So what does that prove? Paul was sent to preach, as Jesus said so (Acts 9). But Paul did baptize some also.
Christ's disciples preached Christ crucified, Faith on Jesus Christ and baptism for the remission of sins. That of course couldn't be in effect until Jesus actually died on the cross and The Father raised Him from the dead.
3) The Holy Ghost
The twelve preached the receiving of the Holy Ghost upon baptism (Acts 2:38).
Paul preached that the Holy Ghost was received upon belief (Ephesians 1:13).
That's misleading. Peter in Acts 2:38 did not actually say the receiving of The Holy Spirit would happen immediately upon water baptism. One would have to insert that idea there, because we have other Scripture examples where some were baptized of water but didn't yet know Jesus had died and was raised, so when they heard about Jesus The Holy Spirit then came upon them. And then with others they received The Holy Spirit BEFORE baptism.
So clearly none of that has anything to do with a dual-gospel idea.
4) The kingdom
The twelve preached the kingdom gospel of the earthly Davidic kingdom (Luke 9:2 Luke 9:6).
Paul spoke of a heavenly kingdom (2 Timothy 4:18).
Another cult misleading. Paul preached the 'kingdom' too, many times (get a concordance, do your own homework).
5) The resurrection
The twelve preached Jesus raised from the dead to sit upon the throne of David (Acts 2:30).
Paul preached that Jesus was raised for our justification unto eternal life (Romans 4:25).
That reveals a basic lack of Bible study. Jesus was promised to sit upon the throne of David, both in the OT and the NT. And David's throne was an earthly throne, which is where Jesus will return to reign, which is also written. No excuse for just brushing over this. When you see men do things like that, then you 'know' that is nothing but a CULT.
The 'hireling' preaches for money (John 10). God didn't call them. Like wolves they prey on congregations. That is why they make up whole doctrines to draw brethren out of the money in their pockets.