FYI...If anyone needs help with any of these, let me know. It is God's work in my life to help people being attacked spiritually. I have already overcome the Evil One.
Oppression: Dark, heavy, cold, looming, ominous, shadow, surrounding you (outside your body), literally pressing in on you from every side. It is the presence of Satan (the one who remains outside of God). Without the Holy Spirit of God inside you, the Devil's oppression will physically FORCE you to your knees. Your only hiding place, defense, "strong tower", refuge, and/or place of safety from demonic oppression is the Word of God. It's the "Word of Christ" which we need to "dwell in us richly". If you have the Holy Spirit already, open a Bible and read it out loud. The oppressor will leave after some resistance. If you do NOT have the Holy Spirit, ask the Father for Him in Jesus' name.
Torment: The Enemy's "Fire arrows" of terror, hate, lies, rage, fury, fear, doubt, blasphemy, etc,. These can sometimes be physical torture, but are more often mental thoughts that can literally feel like sharp, terrifying "stabs" of a knife in your mind, soul, spirit, mind, or body. The Enemy fires them into the mind like flaming, poisonous arrows, and they are also kind of like black crows that nest in the branches of your "tree" (mind). They have to be "shaken" out of your mind's branches, or pulled out and healed by God. This can be hard when they come in swarms. The defense against satanic torment is the "helmet of the Hope of Salvation" and the "breastplate of righteousness". NOTE: Mental demonic torment, including satanic thoughts, IS NOT the same as demonic possession. Born-Again believers can be Oppressed and Tormented, but NEVER demonically possessed.
Possession: An evil spirit (other than the individual) living inside the heart/soul (not simply the spirit or the mind) of that individual. Demonic possession is rare, even in people with mental illness. Only about 3-5 of every 100 mentally ill people are demonically possessed. The demonic spirit will ALWAYS come to dominate the person, because angels are stronger than people. Demonic possession occurs the same way thieves/murderers enter a house.... they overpower the "man" of the house, come in thru doors or windows (eyes/ears), or even trick the "homeowner" to let them in, posing as "aliens", deceased "relatives", or even appearing as angels of light to the person. Without the Holy Spirit, any person is in danger of being possessed by Satan, and they are ALL under Satan's influence in some way or another. However, once a person has been "born of God", God's Spirit lives in the person's soul/heart, and no evil spirit can ever again enter that persons "house" Soul because the Holy Spirit is the "Strong man" and the "Gift of God" that He calls "irrevocable" and Jesus said "A thief must first bind the 'strong man of the house'" before the thief can rob, kill, and destroy" it.
My experience is #1, I've overcome Satan himself. Also, it comes from 32 years being in Christian circles, 600 memorized Bible verses, 22 years as a born again believer, 12 years of mental illness (6 years successfully treated), at least 6 different month-long psych ward visits (every major hospital in Indianapolis), and THOUSANDS of God's miracles, healings, personal lessons, friends and family with the disease,....