Using 2 droplets for dev/staging and for production.

I’m about to get my first Digital Ocean droplet, but I have a few questions. Thanks in advance for your answers, this forums seems really great.

I’d like to have one droplet that will have a git server, MySQL database, and possibly staging environment.

Later when I’m ready to deploy my Rails app I’ll get another droplet just for Rails/NGINX/Passenger, etc. which will be the production environment.

Specific questions:

1. I have only one domain name, which will be for the production droplet, so how do I communicate with the dev/staging droplet? Does Digital Ocean give me a unique IP for the dev/staging droplet?

2. If DO does give me a static IP for my dev/staging droplet, how do I get my Rails app (on production droplet) to use the MySql database that is on the dev/staging droplet?

3. Can I use Phusion Passenger to deploy to both the dev/staging droplet and to the production droplet?

4. If I only have one domain name (for the production droplet), how will I access my Rails app deployed on the dev/staging server? Do I use some path that includes the DO provided static IP?

Sorry if this is a bit of a NOOB question, but I’m excited to have found Digital Ocean, and want to see if I can do what I’m hoping for. Thanks!