The Pit
Remember that Revelation is a symbolic book, so the "pit" and the "chain" are symbols of the fact that Satan is not able to deceive the nations as he had been allowed to. In other words. the "pit ' isn't a literal, physical place, where Satan currently resides. It's a metaphor for the fact that
having defeated him, Christ has him under his control and has limited his power. Satan is not now able to have total control over the nations. the gospel will go forth in great power. The way this is put in Mat 12 is that since Christ has "bound the strongman ' he (Christ) is now able to plunder his house. That is what is being communicated in Rev 20.
With that in mind we also recognize the fact that although Satan is "bound" and is therefore limited in his power, he is still active in the world. He is issuing orders from his prison cell (so to speak), or is like a chicken with its head cut off - he's already defeated but is still thrashing about. In fact, he is thrashing about because he is defeated (Rev 12:7-12). So, his "roaming around like a lion" (a metaphor itself) refers to his last ditch efforts to do as much damage as he can.
So, we recognize both of these truths. The Devil is defeated. but his defeat has not been finalized like it will be at Christ's return. He's been defeated but his final penalty has not yet been inflicted upon him. He is not able to stop us and yet he remains our enemy against whom we still
fight. It is part of the "Already - Not Yet" tension in which we live after Christ's resurrection but before his second coming.