How do we tell the difference between genuine and not so genuine? Christians in the Bible have certain traits that identify them as Christians. And this is because God first brought about a change in their hearts. Before experiencing Christ in their hearts, they thought and acted according to their sinful nature. After experiencing the inner change through the new birth, they began thinking and acting according to their new holy nature.
But many today suppose that if you do what Christians in the Bible do, you will become one. Based on free will experiences of everyday life, they naturally view the Gospel as a contract or sacrament God offers to all who partake. When it is really an announcement directed to all who believe. Telling them of their salvation and telling them to repent and be baptized.
But since Christians believe in Jesus, repent and are baptized, these turn Christian acts into sacraments. That is, if a person chooses to partake of the key sacrament for salvation, belief, it will make them a Christian too. Not knowing that belief in Jesus is an effect of him living in the heart that needs no choice or sacrament Romans 8:16. But to them, it is all about choosing to do what Christians do naturally as conditions for salvation.
The key to understanding the difference between genuine Christianity and its "knockoff" versions, is how we view Christian traits. Salvation is of grace. And so when we read verses that say "whoever believes, God will save” as a trait of those God saves, and not a condition people must meet in their own strength, two different religions become obvious. The one of grace, the other of works. Both claiming to be Christian.
Because salvation by grace controls how we interpret other scriptures, and works cannot save anyone, we can rule out any sacramental grace or works/grace version. Whether the sacrament is the popular decisional regeneration model or the historic baptismal regeneration model, grace is not grace unless it remains unconditional.
We should not assume all who trust in their decisions or baptisms are lost. Since grace is unconditional. But knowledge of the Gospel saves us from many pitfalls.