Then thanks for you concession speech, as you initially argued "one gospel," one piece of good news, and that the 12, including Judas, preached the 1 Cor. 15:1-4 KJV good news, per the Lord Jesus Christ. But they did not preach the 1 Cor. 15:1-4 KJV good news, as Paul preached, as you concede that the 12 knew NADA "about it beforehand." And yet, for three years, or so, while clueless as to the impending, prophesied death/burial/ resurrection, the foundation of the 1 Cor. 15:1-4 KJV good news,they, including Judas, were preaching "the gospel of the kingdom," the good news re. the prophesied kingdom of heaven upon the earth.
Thus, your argument is refuted, as there is more than just one piece of good news/gospel in the book-the context telling us what gospel/good news is being referenced/discussed.