How Can you retrieve messages that have been deleted?
Retrieving messages that have been deleted
iPhone 13, iOS 15
See Delete messages on iPhone - Apple Support
What does iCloud back up? - Apple Support
2. When you use Messages in iCloud or turn on iCloud Photos, your content is automatically stored in iCloud. That means that they're not included in your iCloud Backup.
It depends if you had turned off messages from iCloud in iPhone initially Use Messages in iCloud - Apple Support
If you turn off Messages in iCloud on an iPhone, iPad, or iPod touch, your message history will be included in iCloud Backup. If you set up an Apple Watch for a family member, Messages in iCloud is the only way to back up messages.