Both teachings were in error and were corrected and ended. There isn't some magic seal, statement, standard protocol, or circle dance the prophet needs to do to put an end to it. It was ended. I don't know why you are hung up on some technicality that nobody cares about but you.
The process you are describing here for the development and implementation of policy is that of a secular organization.
The LDS Church is a man-made organization comprised of men leading it. I'm sure there are Mormons on here that think otherwise, but honestly you can't explain any of the many changes in it unless you realize that.
If the LDS Church makes its way by trial and error, as you have described, what need does it have for God?
Again, learning and adjusting is part of being human. The idea that the LDS Church has it all correct and is run by "God" is laughable. There is a great deal that is wrong with it and ignoring that and not making changes to it is silly. In fact, the problem with the LDS Church is it isn't adaptable enough IMO.
Is it not God's job to lead the Church so as to make it more honorable, trustworthy and reliable than a secular organization?
No. The LDS Church is just an assocation of members where you can discuss similar doctrines, help one another, and so on. It is not God's job to force people to be perfect or even make good choices.
What happened to the direct communication with a divine being in the management and operation of the church that is the only representative of the eternal and everlasting gospel on the Earth?
It is always there, but it is hardly something the LDS Church has a lock on. The responsibility of direct communication is between us and God. The whole reason that the LDS Church was formed in the first place was because preachers were teaching whatever they "felt" was best instead of encouraging their listeners (and they themselves) to speak with God directly instead. The LDS Church is a perfectly fine Church if you realize that since you can filter out what is true and dispose of what is false. However, it is also not "perfectly" fine when it strays from this ideal and encourages people to listen to only LDS Church preachers instead (which has happened).
What happened to the God whose job it was to never let The Prophet lead the Church astray?
That is just a false doctrine promoted by the brethren and is just silly. God won't lead you astray - that is not true for any man.
Starting with "I see but one" Joseph Smith, and continuing pretty much unbroken through "Mountain Meadow" Young, "Manifesto" Woodruff, "I don't know that we teach that" Hinkley and "Prop 8" Monson, the LDS Church has a terrible track record in terms of the honesty and integrity of its leaders.
"Lying for the Lord" is a practice that has been openly discussed and practiced by Church leaders and, as a consequence, is widely associated with the LDS Church.
When you make the kind of claims you have so far on this thread, one is left to wonder if you really have a fact-based understanding of the way in which the LDS Church is lead and operated.
You are under the impression that the LDS Church is something it is not. The same can be said of the men that lead it. They are fallible men, and as human as anyone else and not God. And the LDS Church is only true as far as it leads people to God. It is also false when those in it teach and lead people away from God and doing what is right. The point of the whole thing is to get you to speak with God yourself and use your good reason and sense to make up you own mind. Mormons that rely on others to do the thinking for them (or the speaking with God) are just fooling themselves.