St. Cassian
Both Peter and Paul were martyred in Rome.
Yes, Christopher was martyred about the year 251.
Yes, he was martyred for being a Christian.
George was martyred. He martyred no one.
Saint Agnes was martyred in Rome.
Saint Pedro Calungsod was martyred in 1672 at the age of 17.
Yes, both Saint Lorenzo Ruiz and Blessed Pedro Calungsod were martyred for their faith. Saint Lorenzo Ruiz was martyred in Japan in 1637, while Blessed Pedro Calungsod was martyred in Guam in 1672. They are both revered as Filipino martyrs and saints in the Catholic Church.
Saint Isaac Jogues was martyred in America - Canada.
Euphemia
The female Christian saint martyred at Chalcedon is Saint Euphemia. She is venerated as a martyr and saint in the Eastern Orthodox, Roman Catholic, and Oriental Orthodox Churches.
No, Saint Helen died of natural causes and was not a martyr.
Saint Lucy was about 21 years old when she was martyred and became a saint.