Context is important. Romans 11 is not referring to Christianity.
Rom 11:17 And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree;
Rom 11:18 Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee.
Rom 11:19 Thou wilt say then, The branches were broken off, that I might be graffed in.
Rom 11:20 Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
Rom 11:21 For if God spared not the natural branches, take heed lest he also spare not thee.
Rom 11:22 Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off.
Rom 11:23 And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again.
I Corinthians 10 is not about losing your salvation but about learning to avoid sin for although God does not count it against you, it does open up the believer's life to more of Satan's attacks
1Co 10:6 Now these things were our examples, to the intent we should not lust after evil things, as they also lusted.
1Co 10:7 Neither be ye idolaters, as were some of them; as it is written, The people sat down to eat and drink, and rose up to play.
1Co 10:8 Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand.
1Co 10:9 Neither let us tempt Christ, as some of them also tempted,
and were destroyed of serpents.
1Co 10:10 Neither murmur ye, as some of them also murmured,
and were destroyed of the destroyer.
1Co 10:11 Now all these things happened unto them for ensamples:
and they are written for our admonition, upon whom the ends of the world are come. 1Co 10:12 Wherefore let him that thinketh he standeth take heed lest he fall.
One can receive the Spirit of eternal life without being made eternal as OSAS claims.
When we are clothed with
immortality then yes we can not become lost.
Until then---
Heb 3:12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
Heb 3:13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin.
Heb 3:14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;
LA