How can I unlock iCloud from a device

See this article.

How to remove Activation Lock - Apple Support

All of your photos on all of your devices

iCloud Photos works seamlessly with the Photos app to keep your photos and videos securely stored in iCloud and up to date on your iPhone, iPad, Mac, Apple TV, and on iCloud.com. If you take a photo on your iPhone, for example, you can see that same photo on your other devices and on iCloud.com, too. Try this