1. Yes, DS4.5 Autofit does transfer the morphs

2. Expressions are figure-specific, like any morph.  If you want to use Gen 4 or Gen 3 expressions on Genesis, you need to transfer them with GenX like any morphs.

3. You can use M4's bits on M4, or parent them to Genesis.

 

You don't have to use Genesis, you can use older content in DS4.