Will updating to iOS 14 delete anything?

In addition to making the process a little easier when you want to update the OS, it also will keep you from losing all your favorite photos and other files if your phone is lost or destroyed. To see when your phone was last backed up to iCloud, go to Settings > your Apple ID > iCloud > iCloud Backup.

Will iOS 14 delete my photos?

Once you restored your iPhone with the selected iTunes/iCloud backup, all the current data on your iPhone will be erased and replaced by the content in the backup. This means the new messages, photos, contacts, and other iOS contents are not included in the backup will be erased.