The "Privacy Policy" agreement. This is required by law.Use this agreement to inform users about your privacy practices and what kind of personal data you collect from users.
If you collect any kind of personal data from your users (e.g. email addresses, first and last names), you're required by law to have this agreement.
The "Terms and Conditions" agreement.This is optional but recommended. Use this agreement to set the rules and guidelines for users when they register an account with you.
You could add the Return and Refund Policy in your Terms and Conditions rather than having a separate agreement on returns.