Continuity of instances across key frames

I have a MovieClip that exists in a few key frames along a layer in my timeline.

In AS3, in my Document Class code, I reference it by instance name. I change some of its properties. I realize the Document Class code only sees the state of things in the first frame.

I find that later on in the movie that MovieClip’s properties are as I had set it for the instance in the first frame. The ones in subsequent key frames don’t have instance names.

I am not trying to solve any particular problem here but just trying to understand continuity of instances. Is the instance in the first key frame also the instance in subsequent key frames. (It’s kind of like a Bill Clinton-esque questioning of the defition of the word “is”). I was surprised that the property changes I made in the first frame carried over. I thought if the same MovieClip was dragged to different key frames they would be different instances.

What if we want them to be seperate instances?

I am pretty good at ActionScript because I’m a programmer, but I don’t understand Flash overall very well. The timeline especially is an enigma to me.