With iSunshare iDevice Genius, you can clear crash logs, pictures, and large files, download failure caches, and voice memos to free up space. At the same time, you can uninstall the unused apps to get more space.
Yes, you can double click to preview the photos. Besides, you can export the photos to your computer for backup.
iDevice Genius can help you to scan and find out all large files which exceed 5MB on your iPhone, such as videos.
It depends. If you have already exported the photos to your computer or created a backup of the iPhone, you can restore it via iTunes. If there is no backup for the photos, you can never find it back.