I think you are both right
but then I do not think that the Book of Revelation is trapped in one time period
but is all time
including the last time
Revelation 1:1 says the book is about “things which must shortly come to pass”; of course a short time with God is a millennium for us.
As for the Beast, that was first mentioned in Daniel; it is denoted by the fourth beast, which has an identical description to the beat in Revelation 13.