Q: Access to photos in photo.app

iCloud Drive contents can be accessed via any web browser (on computer and iDevices) by signing in at iCloud.com.

On a computer, the iCloud Disk icon can be accessed via its icon in any Finder window sidebar.

On an iDevice, launch the iCloud Drive app.

If you enabled iCloud Photo Library, you should move all your images into the Photos app. Easiest to do on a computer.

Suggest reading this article as it will explain how iCloud Photo Library works.

iCloud Photo Library FAQ - Apple Support