If some science lab announced tomorrow morning that they had cracked an 'immortality serum', you know what would happen. Everyone would fight for first dibs. The Rich and Powerful would get priority, and then suddenly realize that the world would fill up too fast, and limit access.
If, for the sake of argument, everyone was given eternal life anyway, by means other than Paradise, under Divine Rule? Then what? You'd spend eternity working off debts that somehow kept growing for all eternity, the way student debt does now. Someone would raise the cost of food dramatically, because 'you can't really die, so do you need to eat, given how many mouths there are to feed?'
The only way to be wealthy now is if you inherited a huge fortune from your parents. if they never die, do rich kids spend eternity on their old allowance, working in Daddy's company, with no chance to ever do anything different?
If the world could have granted eternal life even 200 years ago, the Class Systems would ensure that slaves would never be freed, and spend eternity under the whip. The Aristocrats would despise poor people even more than they did already. The powerful would find some way to exploit the absence of death for their own profit. Even the very patient, who saved little coins, one at a time, for a billion years, and eventually have their fortune? imagine the bitterness that would come from centuries of denial, prejudice...
If the secular world could have granted eternal life in the time of the Pharaohs, or the Emperors, or literally any point in human history, then society would have become static. With the same people in charge forever, nothing would ever change from the way it is. If a King, or a President could rule for longer than a Term Limit, or even a lifetime, the world would become fixed.
Watch any period piece, any move set as recently as the 90's, and you'll see how times have changed. You nod and say "That was how we thought back then." Now imagine that you never get to see any 'new' faces on television, or hear any new leadership ideas.
Believe me, Eternal Life is the least of what will make it a Paradise.
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As to the other question, "Would you step away from God's Rule if you could, without losing His Promise?"
I don't know. Probably a few more movies/books/video games I'd normally avoid. It's not like going out to bars, or smoking a cigarette holds any appeal to me.