If I get confused again by the same question I asked before, should I unaccept the answer or ask a new question exactly duplicated?
I think the key to successfully asking a different question is going to be making it different. Say you first ask:
And someone tells you "3 hours" and you accept it. Then later you learn that the route they are talking about involves using a different vehicle than the one you own, and you can't drive on that route.
At this point if you edit your question you will make all the answers invalid, so don't do that. But (and this is really important) don't just go open a new question and type:
It will be closed as a duplicate. Give the question some time and thought. (I notice that you have a habit of editing comments and generally changing your mind that makes conversations hard to follow.) Ask your new question something like this:
Even include a link to your older question. When you do this, you reduce the chances of being closed as a duplicate, because you're explaining what is different about this question and the other one.
If you are still confused by the same problem and if the accepted answer doesn't help then you should have never accepted it in the first place. However, if you are in this position, unaccept the answer and either edit the question to provide more information so you do get an answer that it truly helpful or consider posting a bounty.
However, if your edit would substantially alter the question or if your new problem is related, but different then post a new question linking back to the original and clearly explaining why it's different.