Everybody being different because of age, health, how active ,etc. makes itimpossible for one answer to your questions.
Years ago on a 10 day fast, I worked at a fairly physically demanding job. Then when I came home I would run 2 1/2 miles at about a 7 minute mile. That was then, I wouldn't couldn't do the same now.
If you listen to your body it will answer all your questions for you.