Anyone over 18 can open a PayPal account, except some countries are excluded by the US Government from accessing US domains eg Syria.
Provided you live in a country with access, you can start an account.
You can withdraw cash. What you do is you transfer it to your bank account and then withdraw it from there.
Click on http://www.paypal-australia.com
to read up about PayPal. When you sign up, PayPal will automatically default to your country's PayPal system or if there is none, the the US system.