How to recover photos if deleted permanently?

You can see this:

         If you're missing photos or videos in the Photos app - Apple Support

Basically the above says to look in Recently Deleted and in Hidden. Be sure to check your Library thoroughly-- the pictures may not be where you expect, as dates may have changed. You can use the search field with the date or location.

If you use iCloud Photos,  you can look at Photos in iCloud.com. But they've probably already been deleted there, unless you're very fast.

If you don't use iCloud Photos, but you have Settings>Apple ID>iCloud Backup turned on, then you may be able to recover data from the last 30 days or so at iCloud.com. You should look here:

         View and manage iCloud device backups - Apple Support

This requires you to erase everything on your phone and replace it with the backup.

If you don't keep your own backups to an external drive, then there really isn't any place else to look.

You will have to use the backups you made while the photos still have been on your device.

If you have an iCloud backup of your iPhone that contains the photos you can recover them by restoring the iPhone from the backup. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

The iCloud backup will not contain the photos, if you have been using iCloud Photos, however.

The "Recently Deleted" album is the only safety line offered by Photos. Once the photos are gone from Recently Deleted we are on our own.