If you are a true believer....and fall into sin you are still saved. BUT, the bible tells of the
bema seat judgement of Christ.
1st Cor 3:15 tells us this.....If anyone’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire.
...That individual will suffer loss. They're saved....using todays idiom...by the skin of their teeth.
That is right, the spirit is saved and could lose all rewards, but saved they still are.
Those that lost all rewards, still believed in Christ, so they remain saved based on what Christ did for them making them alive who were dead in trespasses. Ephesians 2
Those that are apostates, don't believe in Christ. Jude gives ample descriptions and so does Peter about false workers.
We have a clear word about the sheep of Christ, they hear His voice, they follow Him, they are saved and will never perish, so then it is eternal life for them. Anyone who says contrary to the sound words of Christ is as Paul says they know nothing and are puffed up.
Paul gives practical advice here of what to do. they have corrupt minds, destitute of the truth, useless wranglings, see nothing you can say will get through to them. Such persons God must grant a repentance or they are doomed, they are captured by Satan to do his will. Thier ears are stopped up and they can not hear so then harken and believe spiritual truths.
1 Timothy 6
3 If anyone teaches otherwise and does not consent to wholesome words,
even the words of our Lord Jesus Christ, and to the doctrine which accords with godliness, 4 he is proud, knowing nothing, but is obsessed with disputes and arguments over words, from which come envy, strife, reviling, evil suspicions, 5 useless wranglings of men of corrupt minds and destitute of the truth, who suppose that godliness is a
means of gain. From such withdraw yourself.