Recovering old messages
how do I recover old messages backed up to my iCloud
iPhone 11, iOS 15
Generally, you can't.
If you use messages in iCloud, iCloud only syncs messages between devices. When you delete a message it is erased immediately.
If you do not use messages in iCloud, you can delete your device and restore it using a backup that may contain the message. You'll lose anything new since the backup was made.