Condensed Version of Opening Post:
1) All that hear and understand the gospel have opportunity for salvation.
Do you think repentance might come into this somewhere? How about faith? Understanding something is not the same as believing it, and believing is not the same as repenting (Acts of the Apostles 8:13, 21).
2) All that hear, understand and learn are given to Christ
So is there some sort of exam to show that one has really understood and learned?. I know you are referencing John 6:45, but our Lord was using the verse to reference Isaiah 54:13, which is pure grace.
3) All given to Christ are saved and will be raised up on the last day.
This is true, but not in the way you think it is.
To be given to Christ refers to God choosing to transfer an individual whose faith God has credited as righteous faith, from the realm of darkness into the marvelous light of the Kingdom of His Beloved Son.
Romans 9:33 says, speaking of Christ,
'And whoever believes on Him will not be put to shame.' So one believes, but then has no idea whether God is going to credit one's faith as righteousness!
'Believe on the Lord Jesus Christ and you will be saved, subject to God overruling and sending you off to hell!'
This spiritual relocation is referred to in scripture using several terms. For example, in 2 Thessalonians 2:13 and 1 Peter 1:2, the transfer into Christ's spiritual body is said to be the sanctification by the Spirit or sanctifying work of the Spirit.
Or, more accurately, those two verses have nothing to say about any 'spiritual location' but refer to the Father's election in eternity.
Another term used to describe the same relocation, is baptism, as in Romans 6:3 where individuals are baptized into Christ.
Can someone really be baptized into Christ subject to God the Father not overruling? I don't think so.
Yet another is the term "called" as in called you out of darkness into His marvelous light, 1 Peter 2:9. Lastly Colossians 1:13 plainly and clearly refers to the relocation as transferred.
Again, this is totally artificial. We were given to Christ before the foundation of the world (Ephesians 1:4) and He has done everything necessary to save us.
"Father, I desire that they also whom You gave Me may be with Me where I am, that they may behold My glory...." (John 17:24). There is no question of any of them being lost.
Where are our human spirits before the transfer? In Adam.
Where are our human spirits after the transfer? In Christ.
Where are our human spirits before we repent and believe? In Adam.
Where are our human spirits after we repent and believe? In Christ.
No need to make it complicated.