trajan
Persecution of Christians, and maybe some others.
He ended the persecution of Christians
Possibly, he stopped the persecution of Christians in Rome, but that may have been just to get their support in battle
Approximately three centuries
Yes they did in secret rooms in their house
The Emperor Constantine made these changes.
After the Great Fire of Rome, in the year 64, Emperor Nero did, perhaps unfairly, blame the Christians of Rome for starting the fire. However, there is no evidence that he persec uted the Christians more generally.
There was a persecution of Christians in the city of Rome in 64 AD. However, it was not an official persecution and it was not legislated. According to Tacitus, a Roman historian, the emperor Nero used the Christians and a scapegoat because there were allegations that he started the Great Fire of that year.
Nero did not "start a campaign against the Christians." In the aftermath of a devastating fire in Rome in 64 AD, rumor had it that Nero had started the fire. To shift suspicion away from himself, he began arresting Christians. Some of those arrested informed against others and, for a few weeks in the city of Rome itself, Christians were tortured in particularly barbaric ways. The historian Tacitus, in his Annals 15.44, describes the persecution and says that the ferocity of it soon created a backlash of sympathy for the Christians. This persecution was short-lived and did not spread beyond the city of Rome.
It appears from historical evidence that the early Christians were largely ignored by the pagan Roman Empire, apart from two brief periods of official persecution after 250 CE, and in the Great Persecution early in the fourth century. When disaster struck, local Christians were sometimes accused of angering the gods, resulting in small scale mob attacks on Christian targets, but by and large it appears that Christianity prospered. Edward Gibbon (The Decline and Fall of the Roman Empire) believes the Christian tradition of widespread and savage official persecution began around the end of the fourth century, as justification for the persecution of the pagans by Christian authorities.
The Bible does not mention any Roman Emperor as persecuting the Church. In fact, there does not appear to have been any widespread, official persecution of the Church during the first century. The only exception to the first-century emperors ignoring or tolerating the Christians was when Emperor Nero blamed the Christians of Rome, probably unfairly, for starting the Great Fire of Rome. Edward Gibbon (The Decline and Fall of the Roman Empire) says that this did not extend to a general persecution of Christians throughout the empire.
325 AD.