Using separate sheets of paper, type, double-spaced, your responses to the following
questions, and include them with your other application materials. (There is no need to attach this page.) Use your best judgment in determining the appropriate length of your essays.
what does mean "separate sheets of paper, type,double-spaced"? whether does it mean answer every essay question at each double-spaced paper? and whether i must answer all 5 questions?

Yes, Answer every essay quesiton in double-spaced paper. Darden essay has not word limit, but it is always suggested to write it concisely.
You can decide by yourself whether you want to write optional essay or not.
Hope it helps!
Good Luck in Darden application!