The means by which we are saved has always been the same. All men are saved through the work of Jesus Christ.
Is this what you mean by the "rules"?
The rules surrounding how we express our commitment to Christ have changed. They must have, given that for half of our history, He had not yet died on the cross.
I was merely using the word you yourself used for the sake of continuity. So you will have to answer your own question. I tend to steer clear of concepts involving rules because I am very much a relationship person in theological terms. There aren't do x and y and you will be saved kind of rules. For one person it might mean believing God when he tells you to sacrifice your son. For another it might mean following some provision of the law of Moses like taking your new born boy to the temple at 7 days old. For another it might mean disobeying the law and for another it might mean believing a street preacher when he tells you about Jesus and in your heart promising that you will go to church and find out more. Whether it happens before after Christ was born is academic.