Absolutely - the same API that drives our user interface is available to you. We provide documentation so you can build a library in your favorite language to talk to IO
Possibly - you can check IO status on the Adafruit Status page.
There's a monitor page built-into Adafruit IO which provides a live view of incoming data and error messages. Keep this page open while you send data to your Adafruit IO devices to monitor data and errors.
The data your store with IO is yours to manage and control. You can download it all anytime and we will never sell or give it away to another company. We feel strongly enough about this that we put it in our IoT Bill of Rights.
If you have any questions or issues with Adafruit IO, post up in the Adafruit IO Forums or chat with Adafruit staff and community members in real-time on the adafruit-io channel on the Adafruit Discord server.