Since the body of Christ is in heavenly places, and the twelve apostles will be judging in the Kingdom on earth, I don't see how he could be in both.
Matthew 19:28
And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon
twelve thrones, judging the
twelve tribes of Israel.
Peter wasn't writing to the body of Christ.
The strangers scattered is talking about Jews. We see that here where Jews came from all over to celebrate the Pentecost. Then they were scattered when the persecution began with Stephen's stoning.
Acts 2:5 And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven. 6 Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language. 7 And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? 8 And how hear we every man in our own tongue, wherein we were born? 9 Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia, 10 Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, 11 Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
The church in Jerusalem had elders, just as Israel always had. Still, this is not the body of Christ.
Acts 15:4
And when they were come to
Jerusalem, they were received of the church, and of the apostles and
elders, and they declared all things that God had done with them.