Just some questions:

What is the minimum age requirement for someone who wants to enter a piece of writing for the prize?
What are some personal opinions on a young writer entering?
Does the entry need to be a certain length?
Does it need to be published?

Help if you can.

Here is a website that lists the guidelines and forms:
The Pulitzer Prizes -- Entry Forms

Still looking for a minimum age requirement. Can't seem to find it.

I read through all their information and what comes out very clear is that the accomplishment is what is measured. Now you can contact them at their email -
Email: [email protected] and ask your specific question.