Can a person have numerous talents, and focus on each distinctively?

The magnificent Charles Chaplin could perform comedy, write, direct, play violin, and orchestrate music. He did with remarkable results.

Yes. But not everyone has that level of concetration and compartmentalization.

Yes. All you need is some way to quantify it and to measure growth.

That probably depends a lot on the specifics.

Think back in your life and think of things you consider talents. Did you only have one? I remember having several and had no problem focusing on one and then the next at the appropriate times.