@Hi Kosonen,
On the question of chronology, we are in full agreement. Surely the Beast will not be here for 100+ years. It is explicitly stated to be 42 months (Rev. 17:8).
Now the question of the identity of the Beast of chapters 13 and 17.
I think they are one and the same Beast based on these Bible passages: The dragon, Satan, is described in Rev. 12:3 as a seven-headed beast, with ten horns, wearing ten diadems on his head. In Rev. 13:1, the beast is described in much the same way: only the 10 diadems are on ten horns. But since it is explained in Daniel and Revelation that both the horns and the heads signify kings, the difference is a refinement rather than a reason for the difference. An important statement is then made in Rev. 13:4, where it is said that the Dragon gave the Beast his power. In Rev. 13:11 another two-horned beast appears, again speaking as a dragon, and in Rev. 13:12 it is stated that he exercises power, the first beast. Then in Rev. 13:14 it is said that this beast, will make an image of the first beast, which had the wound of the sword, but began to live again. In Rev. 14:9 or 14:11 the Beast and his image, or the "mark" of Rev. 13:16-19 is still spoken of. According to Rev. 15:2 there are to be overcomers over the Beast and the image of the Beast made by the two-horned beast, and finally in Rev. 16:2 there is a description of when the first bowl is poured out on those who have the mark of the Beast and worship his image. And the 5th bowl, according to Rev. 16:11, is poured out on the throne of the Beast. The reaction is that out of the mouth of the Dragon, the Beast, and the false prophet, came three unclean spirits. The number here is numerically limited and besides the Dragon, there is only the first, the seven-headed Beast and then, the two-horned beast.
The beast of Rev. 17:3 is described as having seven heads and ten horns. In Rev. 17:8 the Beast is to come out of the abyss, which brings me back to Rev. 11:8, the basic time sequence is given: first the two witnesses (1260 days) and then the Beast killing the two witnesses after it comes out of the abyss and works for 42 months. In Rev. 17:11, this Beast is the last, for he goes into perdition.
And the end result, in Rev 19:19-20, is the Beast and the false prophet are taken captive and it is specifically stated that the two, are cast into the lake of fire. In Rev. 20:2 the Dragon, Satan, is bound and cast into the abyss and Rev. 20:4 describes the resurrection of those who did not worship the Beast and his image and receive the mark. After the 1000 years are over, then Satan is released from the abyss (prison) and because Satan does not take a second chance, he is cast into the lake of fire where the Beast and the false prophet are (Rev. 20:10).
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The seven-headed Beast is variously described, but derives its form from the Dragon. It is explicitly stated that the Beast, with the Dragon and the False Prophet, as it three entities. The Beast comes up out of the sea (from the abyss = deep sea Rev. 17:8) and wages war with the faithful - killing the two witnesses (Rev. 11:8) and triumphing over the saints (Rev. 13:7).
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Personally, I think the Beast is one because it is well documented. Most commentators agree that this seven-headed Beast is the Antichrist. I find the Antichrist question more difficult than whether there are two Beasts according to JWs-theology. Rather, I understand the two-horned beast, with horns like a lamb (Rev 13:11) because of its designation as a "false prophet" (see Matt 7:15: beware of false prophets who come in sheep's clothing...) to be the Antichrist. The apostle John, in his letters, then identifies the antichrists with the false prophets (1 John 4:1-3), and like the two-horned beast (Rev. 13:14), the antichrists also go astray (2 John 1:7).
Traditional exegesis (as far back as Irenaeus of Lyons) sees the Antichrist in the seven-headed Beast. But I am more inclined to believe that the real Antichrist is the false prophet...
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Later, I want to look at the issue of the Beast and the false prophet through the "lens" of the destruction of Babylon the Great and the identity of Babylon the Great, as this also - in my opinion - helps to clarify roles and relationships. I have written something on the identity of Babylon for about a year now, but I need to finish it...