Neither of them did; they were both martyred.
Paul survived as long as he did on his Roman passport. Peter wouldn't have lasted 5 minutes. Remember, it was circa 45 AD that these dudes were on the march, not 1995. Roma hadn't been admitted to the EU yet.
Yes he did. You've blown Diego's argument that Peter was never to go to the Gentiles out of the water.
Peter was called mainly to the lost Sheep of Israel/Judah. Surely, he had to mingle with the gentiles along the way, but Paul was most certainly the one who wrote Romans and the one who was specifically called to the Gentiles.
Gal 2:7 But on the contrary, seeing that I have been entrusted with the gospel of the uncircumcision, as Peter to the circumcision;