Hi there,
ChatGPT Alpha is an experimental release of ChatGPT. Alpha access is available to testers and those who have applied for it. As for the features you mentioned, like uploading images, files, and generating images using DALL·E-3, Currently the Alpha do not support all this.
Regarding the term “confidential,” I don’t know much, may be @EricGT or @Foxalabs can help.