You will need that for your book. You don't need that for the contest. Choose one to enter, but know that completing the exercise for each protagonist will only solidify your knowledge and connection to each character. Try to have them before you write the book. Free days on Sundays are great to catch up when you have extra protagonists or antagonists.

Or you could join the overachiever crew. Don't know that I recommend it - scope creep is a common side effect.