Ask HN: Help with AWS Beanstalk

Hi everyone, I was wondering if some of you lovely people would be able to share some insight for me.

I want to create a single Sign up form in PHP using Elastic Beanstalk. A one page php file that users enter their email address to sign up and then the php file connects to an amazon database to save the email.

However, I am having a few issues concerning cost and actual understanding so I have a few questions:

1) Does Beanstalk create an instance for me to run the web server?

2) If yes, Is this what I pay for?

3) If yes, how much does it cost to have this running? The file would need to be accessible every second of every day because I cannot control when users will go to the page.

4) I was thinking about distributing the signup page through CDN. Is this worth it for speed or will one page not make any real difference?

I am using AWS Beanstalk because, if I understand correct:

I will only get any charge when someone goes to the page, so if I only get 2 signups I will only pay for the time they were on the page and also, let's say I get 10,000 people visit at once, I read that AWS will handle the spike by managing it all for me.

Correct?