Is regeneration and conversion synonymous?

The first, the one you said referring to our justification, is all the work of Christ and the Triune God, our redemption through His blood, it covers all of God's redeemed from ages past to ages future in the whole wide world and among all of humanity. If the Spirit causes us to understand this and gives us the ability to have even a toehold's grasp of this truth, we understand what words "world", "all men", "all", and such mean, and I say this with no reflection on anyone's comprehension.

The second, the one that refers to sanctification, is where gospel salvation comes in, most especially in the theological and cultural context of the first church when the first believers came from sin and like errors of idolatry, paganism, promiscuity, and self-righteous religions which were all sin and from which the first Christians were to be instructed away from.
Consider the letters of Paul, Peter, John and James to the churches and their instructions and warnings to converts.

Practical justification also comes with their having put their faith in Christ and away from the false gods of their times, just as practical justification follows today's believer who turns away from dead religion which is sin.

The third, deliverance from the presence of sin, is what every born again, Scripture-instructed child of God hopes for. His coming again for His people to take them away into His Father's house.

 

Our conversion experience involves regeneration. Conversion is more general while regeneration is more specific.

My take.

 

You think because you are in the majority that you are correct? The Lord taught that the majority of men will perish, and only a few, a minority would know the truth and be saved.

Matt 7:13 Enter ye in at the strait gate: for wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat: 14 Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.