Where to publish Provider Hosted app's web application?

I am confuse in provider hosted app's publish folder.

My questions are :

1. Can I publish provider hosted web application to any online server or I have to use only SharePoint online(Windows Azure) or Office 365 to publish my Web Application?
2. If I can publish my web application project to any online server how can I get the Client Id and Client Secret for that?
3. How can I create certificate for my app which I want to publish for SharePoint office app store?
4. How much time would it take for Auto-hosted apps to get out from the preview mode?

Any suggestions?

Thank you in advance...!