Can someone who proclaims he has been saved, be kept from becoming a Christian because of his sins prior to that point? Can one cast out demons that corrupted the soul during a life of sin and still try to control ones soul while trying to live like Christ?
The Bible is clear that everyone who calls upon the name of the Lord will be saved:
Acts 2:21 And it shall be that everyone who calls on the name of the Lord will be saved.
Rom. 10:9 that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved.
This promise cannot be blocked or revoked. The Lord is the One Who curses, and He will not contradict His word. This promise is sure because all the sin of a person’s life – both the sin prior to salvation and the sin that is committed after salvation – was paid by Jesus’ blood on the cross.
Rom. 3:22 even the righteousness of God through faith in Jesus Christ for all those who believe; for there is no distinction;
Rom. 3:23 for all have sinned and fall short of the glory of God,
Rom. 3:24 being justified as a gift by His grace through the redemption which is in Christ Jesus;
Rom. 3:25 whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed;
Rom. 3:26 for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus.
All have sinned, but the Lord justified us (i.e., declared us to be without guilt for our sin) by our faith in Jesus Christ. Jesus took all the penalty that we deserved for our sin. Notice Paul says in v.25 that God passed over (i.e., forgave) the sins of our past because of Christ. Therefore, we have no fear of condemnation:
Rom. 8:1 Therefore there is now no condemnation for those who are in Christ Jesus.
1Th. 5:9 For God has not destined us for wrath, but for obtaining salvation through our Lord Jesus Christ.
Furthermore, all who have placed their trust in Christ cannot be denied this salvation, since Jesus said that all those who come to Him would never be without Him:
John 6:37 “All that the Father gives Me will come to Me, and the one who comes to Me I will certainly not cast out.
John 6:38 “For I have come down from heaven, not to do My own will, but the will of Him who sent Me.
John 6:39 “This is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day.
Furthermore, the scriptures teach that the Spirit Who indwells every believer is a permanent sealing until the day of redemption:
Eph. 1:13 In Him, you also, after listening to the message of truth, the gospel of your salvation — having also believed, you were sealed in Him with the Holy Spirit of promise,
Eph. 1:14 who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.
Eph. 4:30 Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
Every believer is promised salvation, sealed by the Spirit and cannot be lost from Christ’s grip. The power of the Spirit is not to be compared with the demon world or ever Satan. Satan is nothing but a created being, without compare to the power and authority of the Creator Himself. This is why John tells us not to fear the enemy:
1John 4:4 You are from God, little children, and have overcome them; because greater is He who is in you than he who is in the world.
Therefore, the demon world has no power to disrupt the promises of God to every believer. The Spirit holds us and assures us that we will be resurrected into eternal life. No curse spoken by mere men or demon can interrupt the plans of God as Paul said:
Rom. 8:31 What then shall we say to these things? If God is for us, who is against us?
Rom. 8:32 He who did not spare His own Son, but delivered Him over for us all, how will He not also with Him freely give us all things?
Rom. 8:33 Who will bring a charge against God’s elect? God is the one who justifies;
Rom. 8:34 who is the one who condemns? Christ Jesus is He who died, yes, rather who was raised, who is at the right hand of God, who also intercedes for us.
Rom. 8:35 Who will separate us from the love of Christ? Will tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword?
Rom. 8:36 Just as it is written,
“For Your sake we are being put to death all day long;
We were considered as sheep to be slaughtered.”
Rom. 8:37 But in all these things we overwhelmingly conquer through Him who loved us.
Rom. 8:38 For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers,
Rom. 8:39 nor height, nor depth, nor any other created thing, will be able to separate us from the love of God, which is in Christ Jesus our Lord.
If you have placed your trust in Jesus Christ for your salvation, then no one has “control” over your soul except Jesus Christ.