This is one of
those passages where opinions vary greatly. What I can offer you is what I have come to understand from this passage which is a view held by many (most?) Reformed conservative exegetes.
1. To "fall away" is basically to repudiate one's profession of faith and/or the essential doctrines of Scripture.
2. Must all five conditions be met? No as they are not "conditions" but rather evidences expressed by one's life.
3. The "Prodigal" wasn't saved to begin with. He eventually, by God's grace, came to repentance and returned as a 'new man' (in Christ). Secondly, there is no biblical teaching to be found as to "re-dedication". This is akin to the modern heresy of "The Carnal Christian Theory" which is mentioned in this excellent article here:
Decisional Regeneration.
4. Now, as to what the passage does teach... I believe, along with myriad others, that the writer is addressing a group of people who have not been regenerated, i.e., they possess a false profession/conversion and
outwardly appear to be Christians for a time. The parable of the Sower (cf. Matt 13:3ff) is a good illustration of this type of individual. This type of person is typically a member in good standing in an organized church; even a pastor/elder or deacon. But for whatever reason, they return to the world and forsake their original profession and the Church. Their rejection is firm and final. Perhaps the person who most exemplifies who this passage is referring to is Judas Iscariot.
Hope this helps shed some light on this difficult passage for you.
