What gospel do you think Peter preached in Acts 10 to Cornelius the Gentile? Was it Grace or repentance.
Paul later in Acts in his sermons (after chapter 15) tells the hearers both Jew and Greek to repent. That can be found in Acts 17 and Acts 20. Then when Paul heads back to Jerusalem he summarizes his ministry by saying he preached all should repent. That can be found in Acts 26.
If you would, continue past the 1 Corinthians 15 quote to this:
1 Corinthians 15:5-11 NASB
and that He appeared to Cephas, then to the twelve. After that He appeared to more than five hundred brethren at one time, most of whom remain until now, but some have fallen asleep; then He appeared to James, then to all the apostles; and last of all, as to one untimely born, He appeared to me also. For I am the least of the apostles, and not fit to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am, and His grace toward me did not prove vain; but I labored even more than all of them, yet not I, but the grace of God with me. Whether then it was I or they, so we preach and so you believed.
Isn't Paul admitting here that all aforementioned preached the same Gospel?
We know that Paul said his commission was not to baptize. I give that double barrels to the Romans. However 1 Corinthians still tells us believers are baptized in water. What changed? Did Peter institute the first believers baptism with Cornelius before Paul started his ministry?
By your view of two gospels, I am assuming you believe the Holy Spirit indwelled both repentance kingdom gospel Jews and Grace gospel believers? Does that make them one or two bodies in Christ? Paul spoke a lot about one Head which is Christ and we are the members of His Body.
I will offer that if we look closely at the historical event of Pentecost and understand the scriptures Peter quotes and links to the death and resurrection of Jesus Christ, it is the same Gospel clearly outlined by Paul in 1 Corinthians 15. Same if we look closely at Acts 3. Later we see Philip leading the Ethiopian to Christ using Isaiah 53. Some call Isaiah 53 the Gospel according to Isaiah. The scriptural evidence is there is one Christ, one gospel (the one He gave see Luke 24), one Holy Spirit and One Body.
You are correct and don’t let others ‘try’ to deceive you as they are deceived. They all preached the same gospel as there is only one for those with spiritual eyes and ears. Lacking that, deception enters in.
I often wondered how there would be a great fallen away, now I get a glimpse at it. Indeed, it is the last days.