Therein lies your error . This is a huge presupposition you have that will colour your entire understanding of the bible. I don't say that lightly. //The ONLY ( Emphasis mine ) change Acts 2 brought was Holy Spirit power to spread the Gospel and edify the church - it had ZERO effect on how we accept, retain, or lose salvation, // This has to to date the saddest comment . Wow !! I'm not sure where to begin with that.
You can't seem to recognize that when it comes to salvation, the only Biblical differences revolved around outward expression: the inward experience has ever been the same.
Noticed how monogamous marriage ceremonies around the world differ from the wonderful to the weird to the downright bizarre, but the inward commitment is still the same? "forsaking all others, till death to us part".