It was unique because it was before the fall. Not a “dispensation” as you believe. We were all born in Adam but we are born again in Christ by faith alone (Romans 5:12).
There have been only two covenants, works and grace, and there is and has always been only ONE olive tree (Romans 11).
The belief of dispensationalism that there are two separate peoples of God and, therefore, two plans for salvation I believe is totally unbiblical. God saved a remnant of Jewish believers, those who had the spirit of Christ within them. The NT gentile believers were an expansion of that remnant.
You still are not seeing the point.
You have agreed that “Eden” is a separate period in the Bible.
I could ask what things made it separate.
Instead, I asked what you would name the phenomenon of “a separate period” in the Bible.
What would you name that kind of defined period?