Ultra-dispensationalism is a heretical teaching among dispensational circles. Although out-of-date, it still pops up. It teaches that the Christian Church only began through the work of the Apostle Paul. As a result of this idea, it says that the believers who lived and ministered during Acts 1-8, or a later time, were not part of the Christian Church, but they were part of some Jewish entity.
Ultra-dispensationalists reject the four Gospels as irrelevant for Christians, since they're about the time before Paul. Hyper-dispensationalism usually rejects Christian baptism, calling it a "Jewish" ordinance not fit for the Gentile church.
Here are some simple reasons why this chopping-up of the Church and the Gospel into severed parts (pre-Paul, post-Paul), and this idolatrous exaltation of Paul above all others, is seriously wrong.
Christ prayed that all His people would be one in Him (John 17). He would be in them, and they would be in Him, as they received the promised Holy Spirit. This was not the experience of OT believers, but it is of the Christian Church.
Jesus Christ is the person in whom the entire Church comes together and is what she is. Hyper-dispensationalism demeans Jesus Christ, and attacks Christian unity, by denying that the Church is what she is in Christ.
Christ instituted Christian baptism before Paul was converted. Baptism is the visible ceremony of entrance into the Christian church, which is comprised of disciples of Christ. Matthew 28:18-20. Paul in his ministry administered the very same baptism to new converts that Jesus Christ instituted. There are not two different baptisms in the Church age (one for Jews and one for Gentiles). Paul's baptisms were the same as the baptisms applied in Acts 1-8.
The apostles were the foundation of the Church, according to Ephesians 2:20. They were already re-authorized by Christ after His resurrection, and fully constituted in Acts 1. Those twelve apostles' names will appear on the foundations of the New Jerusalem (Revelation 21).
There wasn't a Jewish church founded on the twelve apostles in Acts 1-9, and then a new, Gentile "mystery" church founded on Paul's teachings from Acts 9 on. The twelve apostles were the foundation of the Church in its entirety throughout time., with just one cornerstone, Jesus Christ.
The baptism of the Holy Spirit integrates people into the Church, which is the same thing as the Body of Christ (1 Corinthians 12:12-13). The first baptism of the Spirit happened in Acts 2, not through Paul. The Spirit-baptism that fell upon the Gentile Cornelius in Acts 10 was the same as that which fell upon the Jewish disciples in Acts 2.
Christ's death, not Paul's ministry, is when God eliminated all Jew/Gentile distinctions, and created the "new man" which is the Church, according to Ephesians 2:14-16. God assigned Paul a special ministry of learning and teaching about this new Jew-Gentile reality, but the reality itself began at the cross, not in Paul's ministry. God had eliminated the OT Jew-Gentile distinction all through Acts 1-8, but the apostles and disciples needed to learn about it.
Christ instituted the Lord's Table as a perpetual ordinance, for everyone whose sins are remitted through His blood, not just for Jewish disciples. That means the Lord's Table ceremony was for the same universal category of person (everyone whose sins had been remitted through faith in Christ's blood), and it carried the same spiritual meaning pre-Paul and post-Paul.
The ceremony and meaning of the Lord's Table was identical in Acts 1-8 as in Acts 9 and forward. The ordinance symbolically binds the entirety of the Church Age together into one.
Paul said the gospel God had entrusted to him for the Gentiles was the same gospel God had entrusted to Peter, James, and John for the Jews. Galatians 2:7-9. There were not two different gospels, one for the Jews in Acts 1-8 and then a different one through Paul after Acts 9.
God gave us the entire Bible for teaching, reproof, correction, and training in righteousness, and the entire Bible is necessary to be spiritually complete and equipped for every good work (2 Timothy 3:16-17). So this bizarre teaching that says the four Gospels or the book of Revelation are exclusively for the Jews and not for us, comes from Satan, and is designed by Satan to make us spiritually sick.