When I read the New Testament, one thing stands out, and that is that not all the 1st century churches were alike. The church at Jerusalem was not like the church at Troas and Troas was not like Corinth and Corinth did not seem to be 100% like the churches in Galatia. It is clear that at Troas and Corinth the church met on Sunday and yet the church in Jerusalem was meeting daily. The church in Ephesus met in a school if I remember right and the church in Jerusalem met in homes and in the Temple court. From the writings of Paul, some of the gentile churches had similar problems with Jew trying to make Jew’s out of gentile Christians by forcing them to keep the old Law. So not all of the 1st century churches were the same in likeness but they were the same in purpose. That purpose being the gospel of Jesus Christ.
The foundation of all the 1st century churches were the same and that is Jesus Christ. No they did not all look alike and they did not all have the same problems; otherwise one letter could have been passed around to resolve the problem.
It should be noted that my statement does not even consider what the Ethiopian Eunuch’s church must have looked like.
So this topic of discussion now brings me to three distinct but related questions:
1) Is the Apostles Doctrine a matter of salvation or is the Gospel of Jesus Christ what matters for salvation?
2) Did Ethiopian Eunuch have the benefit of the Apostles Doctrine or just the Gospel of Jesus Christ?
3) Were the 3000 who were baptized at Pentecost saved before or after they started following the Apostles Doctrine?