Peter preached faith in the name of Christ..........................
[Act 3:16 KJV] 16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
[Act 4:12 KJV] 12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
John clarifies what believing on his name is......................
[Jhn 3:18 KJV] 18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
[Jhn 20:31 KJV] 31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.
[1Jo 5:13 KJV] 13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
To believe on his name is to believe Jesus is Christ the Son of God, which he is
My point is if one says they all preached the same gospel and if you just believe Jesus is the Son of God, and thats al, thenl thats not the gospel we must beleieve to be saved