Icloud backup

1. If you have turned ON iCloud Photos they are not backed up on iCloud. If you delete on iPhone it is gone from iCloud too.
2. If you have Not turned on iCloud Photos, then they are backed up on iCloud. But if you have turned ON automatic Backup on iCloud, then what iCloud does is, it does incremental backup. That means it deletes what is not on iPhone and adds what is new on iPhone.

In a nut shell iCloud is a copy of what iPhone is, just to safe guard your data for any eventualities.

Other option is take manual backup. And never take a backup again on iCloud. This kills the very concept of backup.

What does iCloud back up? - Apple Support

iCloud backup doesn’t include information that are synced and stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos*, Health data, call history, and files you store in iCloud Drive.

*-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 

Assumption: you are talking about iOS backup.

If you are using the iCloud Photo Library, then yes. Delete anywhere and they're gone, but actually moved into the Recently Deleted folder and you have a chance to get them back.

If you are not using the iCloud Photo Library, then photos are being backed up in the iCloud backup and not removed from the backup if you delete them from the device.

Hello.

It depends. If you are using iCloud Photos, then your content is automatically stored in iCloud. That means they're not included in your iCloud Backup.

If you are not using it, then current changes won't apply to the previous backup. But note that iPhone does refresh the backup when it's on a charger and Wi-Fi network, so you might want to turn off Automatic Backups.