All angels were created by God as mature adults in eternity past. Ab initio angels have no ability to procreate. They have rudimentary sexual organs which subserve distinction of the sexes, and are functionally vestigial. After the satanic revolt in eternity past, all angels who collaborated with Satan were cast out of the heavens of heavens to the Dark Void and starry heavens. They constitute one-third of all the angels in existence at that time(Rev.12:3,4). Thus arose evil angels also called evil spirits or demons. A set of them were dispatch by Satan from the Dark Void to cohabit with human females and to corrupt and hybridize humanity. All the angels that took part in the satanic hybridization programme and their humanoid offspring(Gen.6) are imprisoned in the bottomless pit after the deluge, put in chains under darkness, waiting for the judgment of the Great Day[of the Lord]. “For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;”(2 Peter 2:4;cp.Jud.6).
We know what their sin is; they did not keep their first estate. They left their first estate and cohabited with human females, aside from their first rebellion against God. They are not free to roam the Earth. They are so vile. If allowed to roam the Earth, no single one of us will be able to live right. When these fallen angels, the sons of gods came down from their abode in the Dark Void and Starry heavens, and cohabited with human females, and produced humanoid offspring, the nephilim, evil escalated on Earth. It repented God that He had created man, for the thought of the imagination of his heart was evil continually(Gen.6:5). They will be released to torment the unrighteous wicked for five months during the Day Of The Lord wrath at the blowing of the fifth trumpet(Rev.9:1-12). Their incarceration in the bottomless pit for thousands of years has made them more vile and wicked than ever.
Are they evil spirits? Yes. Are they demons? Yes. Are they the demons and evil spirits operating on Earth today? No. The demons or evil spirits that operate on Earth today are some lower class of fallen angels who did not participate in the Satanic hybridization programme. All evil spirits and evil angels, have one common origin in the Satanic rebellion in Eternity past. “And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads. And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.”( Rev.12:3,4). The high ranking fallen angels and Satan dwell in the Dark Void and Starry heavens. They do not like the Earth. They do not like Hell either, which was built for Satan and his hordes of fallen angel. “Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels:”(Matt.25:41). They rule the Earth by proxy through their subordinate fallen angels. In the middle of the 70th week, they will be cast down to the Earth by archangel Michael and the angels of under his command. They will become very angry(full of wrath), and will perpetrate the Great Tribulation against those who refuse to worship Satan(the Dragon) and the Beast(the antiChrist).
“And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, And prevailed not; neither was their place found any more in heaven. And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him. And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night. And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death. Therefore rejoice, ye heavens, and ye that dwell in them. Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time. And when the dragon saw that he was cast unto the earth, he persecuted the woman which brought forth the man child. And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent. And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood. And the earth helped the woman, and the earth opened her mouth, and swallowed up the flood which the dragon cast out of his mouth. And the dragon was wroth with the woman, and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ.”(Rev.12:7-17).
All fallen angels are spirit beings and have spirit bodies. They do not have physical bodies. They are therefore invisible to man. To function here on Earth they must possess physical objects, which act as transducers which enable them to function in the external physical environment, such as human bodies, animals, birds, trees or other objects like images of men, and animals(idols), etc. Satan can give them physical bodies to become visible and operate here on Earth like those fallen angels who did not keep their first estate(Gen.6). Do not ask me how he does that. There are many ways open to him: but that will be the subject of another Discourse. But know of a surety that Satan cannot creat a human body.
Demons do not have PHYSICAL BODIES. They also do not need physical bodies unless they want to be visible and more effective here on Earth. Although it enables them to function here on Earth, it also places limits on their mobility and functionality. The truth is they are not wanted nor needed here. Their presence here is an aberration and an imposition and infringement on divine order. Demons have spirit bodies. I stated that earlier. Good angels also have spirit bodies. Every spirit being has spirit body. God the Father, Jesus, and the Holy Spirit have spirit bodies. Man has a spirit body which is invisible to the unaided eye. Jesus is the only member of the Godhead with glorified eternal immortal resurrection body. Angels do not have glorified immortal resurrection bodies. It is of a different order; only Jesus and redeemed humanity have glorified eternal immortal resurrection bodies. “It is sown a natural body; it is raised a spiritual body. There is a natural body, and there is a spiritual body.”(1 Cor.15:44). But remember that Jesus is both wholly man and God at the same time. At the rapture, we shall receive our glorified eternal immortal resurrection bodies. At the final resurrection, all unbelievers will also receive spiritual bodies. But hey are of a different kind, unglorified eternal immortal resurrection bodies. We shall see Him as He is, and we shall be like Him. “Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.”(1 John 3:2).
OT saints received theirs(glorified eternal immortal resurrection bodies) at the resurrection of Christ(Matt.27:52,53). Departed saints of the NT who live in paradise in heaven do so in their Spirit bodies. We are like angels in the resurrection because we will not possess physical and mortal bodies and will neither marry nor be given in marriage. “For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.”(Matthew 22:30).
Yes, demons can possess human beings. We must distinguish between demonic possession where a demon takes control of a man’s spirit from demonic oppression and where a demons dwells on or in a man’s body and causes disease or damage or leaves after causing disease or damage, or where the demons manipulates a man’s soul(will, intellect, emotion) by suggestion or forceful harassment, etc.