1. Yes
2. Yes
3. You can add code for Adsense or any other network by modifying the script yourself, but there is no option for ad code in the actual settings, this is only in the paid version.
4. Yes
The simplest way to cost effectively store, serve, backup, and archive a virtually infinite amount of media, content, images, and static files for your apps.
www.digitalocean.com
Digital Ocean Space as a VPS? Yes. Indeed, the demo of the paid edition runs on DO.