Will the reign of the Antichrist and false prophet last three and a half or seven years?

No. That is a number the premillennialists use. First, they use seven years for the tribulation period, and then you have pre-tribulationists, mid-tribulationists, and post-tribulationists, which refers to when they think the rapture will occur. They believe that when Jesus comes back the second time, he will establish a thousand-year millennial reign, a kingdom on earth starting at Jerusalem. It is called millennialism, and it is wrong; there is not an ounce of truth to it. But prior to that second coming they believe Jesus comes back in a secret coming called the rapture, which takes the church out of the world and brings it to heaven. They are not sure whether that comes before the seven years, at the middle, or at the end, but either way there is a seven-year period. That is the premillennial, or dispensational, view. So no, we do not know how long the Antichrist will reign. All it says in Apocalypse 20:3 is that he will create this havoc for a little season. That is all we have got. We can speculate on how long, and I do in my Apocalypse commentary, but it is not three and a half years and it is not seven years. Sometimes they get these numbers from Apocalypse 11, where it says their body shall lie in the street for three and a half days, but that has nothing to do with it; it is simply a number symbolic of the short time period God will allow these things to happen, as opposed to the forty-two months or 1,260 days also used in Apocalypse 11. The extra half just tells you the time is exact, like saying it is 12:30 rather than 12:00. Most Catholics do not have a clue how to put this together, because they have been following these Protestant premillennialists who write all the books on eschatology.