Need some assistance in understanding FBX SDK data structures

Question

I am attempting to convert the animation of some older files over to the FBX file format in order to import them into the Unreal engine. I am currently going through the data structures and see how what I have can relate to the FBX data structures. I have a few questions that I am asking the community to help me in my understanding:

1. Am I able to create the animation separately? As in, do I have to attach a skeleton within the FBX file format? I am asking because Yes, I do have a skeleton for the animation but I would like to be able to extract these separately. Unreal is able to handle combining them both within the program but is it theoretically possible to export the skeleton then the animation? Or do I have to have the skeleton in the animation export in order for the FBX file format to work properly?

2. With that being said, the old animation file does have references to bones. And by reference to bones, I only have the name of the bone that is belongs to. There is no id, just a string of the name. Which is fine. So when I go to build the FBX for the animation, I will create a scene that holds all of the data. Now for the stack and the layer, should I give each bone name it's own stack? Or should I have only 1 stack and underneath that give each bone name it's own layer?

Note: this is only for 1 object. Each scene will only have 1 object that I am animating. There will never be more then 1 object.