Can I preview a photo before I share it with anyone?

Of course — click any photo in the file manager and it opens in a preview view so you can check it's the right frame, correctly oriented, and not accidentally a shot of someone's elbow. Guests get the same kind of lightbox preview when browsing their gallery. It's a small thing until the moment you need to verify whether that one important shot actually made it into the album, and then it's exactly what you need.