How to send questions\upload files for analysis using Copilot REST API?

Question

I would like to know how to do the following using the Copilot Rest API:

How can I ask Copilot tougher questions via API?

Can I also upload files via the API and ask Copilot questions about its content also via the API?

Do I also require Professional License (86$/Month) to send such requests? Is it because I dont have the right license I cant see any information on this under the Copilot REST API reference guide:

https://www.copilot.com/guide/api-docimentation

Thanks