Will my photos that are not backed up be lost

If you have to reset your iPhone and your photos are not backed up, yes, you will lose them. This is why it's important to regularly backup your devices before something bad happens.

That said, if by chance your Sync Photos with iCloud, they will remain in the cloud and can be downloaded from the cloud when your phone is fixed or replaces as long as you use the same Apple ID.

Yes, a device reset will clear all data not otherwise backed up.

Among other options, those backups might be to iCloud backups, or to iCloud Photos, if either or both of those are in use.

If you’re at the juncture where an iPhone or iPad is disabled, the data on the device is already gone.

In general, the only way to indicate that data has value is to back it up, or to be able to easily regenerate the data.

Unfortunately, most of us learn this same, sour lesson sooner or later, and usually by losing important data.