I've a doubt about how to operate.
Try to explain. I read an unanswered post, I know how to help the user so I reply. When is my "work" completed so to introduce the flag "UAResolved"?
When the user reply that everything is ok? As soon I replied? other...
And if the user doesn't reply?
Re: A question
90% of the time I reply to topics, the original poster will not reply back, even if the solution was unsuccessful.
It is completely up to you in how you mark the posts. If you know for sure that you had the right answer, then go ahead and add the tag to the posts. If you are waiting for feedback from the user, then you could wait to add the tag until after they post back. The primary reason for this tag is to help out the "Bump" search filer (in the sticky topic).
All up to you.