iCloud backup delete

re "my data from iCloud won’t be deleted if I first delete the backup ..."

Sorry, I don't understand; if you delete a backup from iCloud the data in that backup is deleted from iCloud.

If you then later do another iCloud Backup, the data on the phone at that time will be in the new backup.

The following may help.

You were originally discussing two phones. If you delete an iCloud Backup of one phone, that has no effect on the iCloud Backup of another phone (in the situation where you have backed up both phones to iCloud). The backups are stored separately on iCloud and what you do to one has no effect on the other.

You can create the new one first or create it later. Backups of each device are stored separately. Either way you can delete the backup of the old phone.

Go to Settings > [username] > iCloud > Manage Account Storage > Backups > the old iPhone > tap Delete Backup.