How many stages in the chain of evolution do we need to model?

At the extreme we might want separate models for every distinct species that is directly in the sequence from some starting species to humans. On the other hand we might be less ambitious and focus on major changes in the mechanisms for copying skills from one generation to the next.

Will the distinct mechanisms cause parallel evolution, and how will these simultaneous changes in skills interact?

There will be parallel and simultaneous changes, but the interaction has to be explored in models.

Not all changes in the evolution of skills go in the same direction. For instance, a calf can stand up, walk to its mother, and feed within minutes. Human babies have lesser locomotion skills at birth, but can handle more complex movements later.