The 5th Kingdom

Revelation 17:10-11
and they are seven kings; five have fallen, one is, the other has not yet come; and when he comes, he must remain a little while.
And the beast which was and is not, is himself also an eighth, and is one of the seven, and he goes to destruction.

Daniel 2

The Head
Babylon (1)

Arms and chest
Medo-Persia (2)

The body
Greece (3)

The legs
the Roman empire and it revised forms
right leg
spiritual roman empire
[this includes kingdoms like the holy roman empire and other kingdoms where the pope has appointed the king] (5)
British Empire (6)
European union (7)

note this part is only speculation

The right foot
The Vatican (8)
The Vatican city is a little horn (small country) which appointed kings that destroyed 3 kingdoms namely Heruli, Vandals and Ostrogoths
Italy (8)
France (8)
Spain (8)
Portugal (8)

left leg
Byzantine Empire (5)
Arabian Empire (6)
The Ottoman Empire (7)

note this part is only speculation

The left foot
Orthodox Israel (8)
Orthodox Israel is a little horn (small country) which captured 3 territories in the 6days war namely the west bank, Gaza and the Golan heights
Turkey (8)
Syria (8)
Lebanon (8)
Kurdistan or Iraq (8)

Did the 5th kingdoms exist before 100AD during the time of John and the Roman empire

Yes both the 5th kingdoms existed in infant form during the time of Apostle John.
The Roman Catholic Church was founded by a few followers of the Apostle Peter who was killed in Rome. The Apostle Paul revered to this group a few times of which 1 Timothy 4 verses 2 to 6 are one of those times.
“by means of the hypocrisy of liars seared in their own conscience as with a branding iron, men who forbid marriage and advocate abstaining from foods, which God has created to be gratefully shared in by those who believe and know the truth. For everything created by God is good, and nothing is to be rejected, if it is received with gratitude; For everything created by God is good, and nothing is to be rejected, if it is received with gratitude;”
The Byzantine Empire did not follow the Roman Catholic religion but the Orthodox Church. The churches John wrote to in revelations all became Orthodox Christians. It is imported to note that evangelist and protestant groups only come to be centuries later once people realized that the doctrine of the roman catholic church and the text in the bible does not match.