The entire Book of Revelation was already fulfilled. The book is about the destruction of Israel, not the end of the world. There are many times John writes about the IMMINENCY of the prophecy in Revelation. Literally the first verse in the book says these things "will soon come to pass".
Why was Israel destroyed? Because Israel had become extremely evil under the Old Covenant, and was even likened to Sodom and Gomorrah (Matthew 10:15). If you are familiar with the Holy Bible, then you know the Pharisees had always found loopholes in the Mosaic Law do that they were able to do all sorts of evil while still technically following the rules. That's why the Old Covenant passed away in favor of the New Covenant, which is acceptance of Jesus into your heart (Jesus fulfilled the law and set an example of everyone of how to TRULY follow the law).
So we look at Revelation 20:10. I'm not exactly sure who the beast and the false prophet are, but one of them is Israel (Remember, Israel was repeatedly cited as evil and treacherous by Jesus). The Lake of Fire was the destruction Israel faced at the hand of the Romans in 70 AD. Jerusalem was literally up in flames according to Josephus, and according to Josephus, over 1 million people died, which is a lot for back then. "Tormented day and night forever and ever" is actually a phrase (Incorrectly translated, BTW) representing TOTALITY, not ETERNITY. Compare this to the Old Testament prophecy found in Isaiah 34:10. Its almost the same exact phrase (NT writers often quoted OT writers) about the destruction of Edom. Is Edom still burning today? No. TOTALITY, not eternity. Jerusalem was TOTALLY destroyed, not one stone was left on top of another (Matthew 24:2).
This is why Jesus let the adulteress go, btw. The Pharisees who wanted to stone her were evil themselves, so it would not make sense to try to maintain order with them when they were already running a corrupt society. Anyone who found loopholes in God's Law would not accept Jesus (Who fulfilled the Law) into their hearts, and therefore would not "flee to the mountains" to escape the incoming destruction as Jesus had commanded (Matthew 24:16). The evil people and evil society were about to be destroyed anyway, it would to make sense to try to uphold their evil ways.
Ill answer any other questions if yoy have them as i find this stuff very interesting