I disagree with most of this, not that I am any authority but the neither are you. The old covenant was given by a holy God who does not make mistakes, what the old covenant said for the people with understanding of that time was truth. We are to be able to read that truth in the old covenant. For example, they were told to cut skin to mark that they were set apart and belonged to the Lord. When that command, (and the command stood as truth) was given in our hearts, we are to mark ourselves as belonging to God without the need for marking our skin. They were to feed themselves with only holy food, not food from garbage. That is still true, but under the new covenant we are to know that the food for our soul is what is put in our minds, not our stomach.
There has never, ever been a time when work has equaled salvation, from the time spoken of in Genesis it has taken blood given by the Lord, yet you say that under the old covenant they taught work instead of faith. They had such faith in the Lord that they accepted the blood of animals as sacrifice for their sins, they weren't told it was the symbolic blood of Christ, they took it on faith.
Don't take my word for any of this, go to scripture. You will not find any scripture saying God took back his errors. God is holy, it tells us, God is perfect not the imperfect God you are telling of.