There is a checkbox in Task information that allows you to mark a non-zero day duration task as a milestone. Is that what you mean by "a milestone (activity with zero duration) with different start and finish dates"

I'm afraid I don't understand what you are asking. How many tasks are we talking about - I see BB, AA, B. Can you please try again? Project will pay attention to link relationships and attempt to move successor task progress where it's logical. Please attach a file or a picture of what you're talking about.