Peter's meeting with Cornelius is a fascinating proof of the Kingdom message, and the 12 knowing they must go to Israel first, before they went to the entire world. Read it carefully and you will see that Peter was reluctant to go there at first, and had to explain his actions to the other apostles. What is THAT about, if they all understood they were to take the gospel to all the nations?
What do you consider to be God's word? The selection of Scripture by the Catholic Church? The selection of Scripture by Martin Luther? The dictation of God to Moses?
And God's word says plainly that until Israel is temporarily blinded and set aside in Acts 28, Peter and the 11 agreed with Paul to confine their ministry to Israel. (Galatians, Chapter 2). Where they MAY have gone after Acts 28 does not concern us here, for by that time the kingdom program was fully set aside.
Are they not set aside now? And why does the destination of any particular Apostle not concern us? The argument here is that they never ministered to the Gentiles, most vehemently. Secular and post New Testament reports give some pretty good documentation of their destination. Andrew went up as far as Russia and began their conversion. Peter was the first human to raise somebody from the dead and also the first human to convert somebody to Christianity. And he was not Jewish.
So what does this mean? It means that the history of the world and of Christianity is not entirely contained in the 73 books of the Bible.