How to delete files/photos one by one from iCloud?

See the article https://support.apple.com/en-in/guide/icloud/mm3b7fcd0c10/icloud

https://support.apple.com/en-in/guide/system-information/syspf5a64aa6/mac

https://support.apple.com/en-in/guide/icloud/mm08b49040b5/icloud

For a single file / photo tap it and click on delete , hold shift key and tap the photos / files to get selected , and then delete them .

If you go to www.icloud.com and sign in with your appleID, you can open photos there and delete the ones you don't need anymore. If you want to delete them immediately , delete them also from 'recently deleted'

If you use iCloud photos on your Mac, iPad and iPhone, you can also delete them there. iCloud is a syncing service

Select by clicking on the photo and delete