Yes, You can record slow-motion videos from Galaxy A8 Star.
Yes, Samsung Galaxy A8 Star does have the metal frame.
Though Samsung has not confirmed about the Corning Gorilla Glass support for the Galaxy A8 Star but we suggest you to check this video to know how durable display is.
Samsung Galaxy A8 Star comes with 9W / 1.67 Amp charger. It has a USB Type-C port and charges quickly.
Yes, Samsung Galaxy A8 Star does have the face unlock. In addition, it also has a fingerprint scanner.