The essence of the sages’ sermon

Hello Rabbi.

When the Sages used thirteen criteria to deliver halachic sermons (including sermons on the pronunciation of letters and words and other grammatical and syntactic rules), were they actually aiming for a final answer that was already determined before the sermon?
I am not referring to the well-known debate about whether the sermons are references or whether they really arrived at the law through them. Rather, assuming that they arrived at the law through them, I ask whether there is a final answer that the Sages are trying to reach? An answer that is written on a note with the Blessed One and the Sages are trying to hit the mark, or is there actually no such result and the sermon actually creates the law, which the Blessed One did not aim for at all, and has no need for itself at all.

If we say that there is a final answer that has already been determined from Sinai, the following things are not clear to me:
A. It follows that until that sermon was required, the people of Israel never observed this law, even though it was in God’s will at the time of the giving of the Torah, or: Why didn’t God, the Blessed One, say this law (“the final answer”) immediately upon giving the Torah, and waited for many generations until a sage arose to require the sermon, why did God allow us to supposedly transgress His will for hundreds of years?
It is clear that we are “forced” (or completely exempt) in this matter, but it is still not clear why God gave the Torah in this way, that there is a certain law that must be observed and it was never observed until the generation of the Tannaim, for example, what is wrong with the original Torah of Moses, that it required God to give us thirteen virtues and bring forth new things through them.
B. How is it possible that hundreds of years have passed since the Torah was given until a Tanai scholar arose and demanded this sermon (again, assuming that this law was not observed until his time), what led him to demand it? After all, he is aware that this law was not observed in the days of Moses, so how does he think that he is now renewing something that was never practiced (it would seem possible to answer this by saying that at the basis of every sermon there is an assumption that in the days of Moses this law was observed, and it was just forgotten over the generations, or that it became distorted, but I understand that the rabbi does not say this and that he has solid sources that in the days of Moses there were only a few laws).
If we take, for example, the teaching of the 13 Virtues on the ways of carrying a woman (in a sheter and in a beyah), if we say that in the days of Moses this law did not exist, and they sanctified only with money, and if someone sanctified a woman with a sheter, then they ruled that she was not sanctified (and permissible without a get), it follows that there is a real change in the Torah here due to the sermon of the 13 Virtues, so what is the will of God, blessed be He? And what is the point that His will changes when a sage arises and demands a sermon. And if we say that even in the days of Moses they sanctified in 3 ways, then we will be forced to say this about all the laws, and it follows that Moses our Rabbi received a very large part of the Toshab’a that we know today (without being a rabbi).

On the other hand, if it is said that the sermon is not aimed at a specific answer, it is difficult for me:
A) What is there to disagree with about someone who preached with the 13 virtues? (B”D contradicts the words of B”D before if it is greater than it…) After all, there is no specific thing that is true and something else that is not, but rather it is only important that the inference from the 13 virtues be free of contradiction, and that is enough. What is the point, for example, of making a different equal derivation and the like, after all, there is no “truth” here, but rather the sermon is trying to weave.
b) As in the first part, again the essence of the sermon is unclear, why was the Torah given in this way, in a way that it would develop over the generations?

Sorry for the length.