Those with a sinful lifestyle are not, indeed cannot be, believers.
Where, perchance, do you get you ideas from? Because there are no verses or passages that say this. In fact, quite the opposite:
1 Cor 5-
1 It is actually reported that there is sexual immorality among you, and of a kind that even pagans do not tolerate: A man is sleeping with his father’s wife.
2 And you are proud! Shouldn’t you rather have gone into mourning and have put out of your fellowship the man who has been doing this?
3For my part, even though I am not physically present, I am with you in spirit. As one who is present with you in this way, I have already passed judgment in the name of our Lord Jesus on the one who has been doing this.
4 So when you are assembled and I am with you in spirit, and the power of our Lord Jesus is present,
5 hand this man over to Satan for the destruction of the flesh, so that his spirit may be saved on the day of the Lord.
9 I wrote to you in my letter not to associate with sexually immoral people—
10 not at all meaning the people of this world who are immoral, or the greedy and swindlers, or idolaters. In that case you would have to leave this world.
11 But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people.
12 What business is it of mine to judge those outside the church? Are you not to judge those inside?
13 God will judge those outside. “Expel the wicked person from among you.”
2 Cor 12-
20 For I am afraid that when I come I may not find you as I want you to be, and you may not find me as you want me to be. I fear that there may be discord, jealousy, fits of rage, selfish ambition, slander, gossip, arrogance and disorder.
21 I am afraid that when I come again my God will humble me before you, and I will be grieved over many who have sinned earlier and have not repented of the impurity, sexual sin and debauchery in which they have indulged.
2 Thess 3-
14 Take special note of anyone who does not obey our instruction in this letter. Do not associate with them, in order that they may feel ashamed.
15 Yet do not regard them as an enemy, but warn them as you would a fellow believer.
All of these passages were addressed to believers.
Those who sin and do not repent die!
Why do you assume "death" means eternal death? The NT is full of examples of believers who died physically under God's hand of discipline because of their sins/lifestyle.
(Ezk 18:4, Rom 8:12-13, 1 John 2:3-6) Believers purify themselves even as Jesus is pure. (1 John 3:3)
No, believers ARE purified (passive voice) when they confess their sins. 1 John 1:9
Jesus Christ has conquered sin and given us the power to meet the full requirements of the law, that is, to stop sinning, (Rom 8:4) and if we do not we are none of his! (1 John 3:10)
Doug
Nope. Every believer has been SEALED with the Spirit, which is a GUARANTEE for the day of redemption. Eph 1:14
How would you twist that into something it doesn't say?