Yes, Samsung Galaxy A8 Star does have the 3.5 mm headphone jack.
Yes, You can record slow-motion videos from Galaxy A8 Star.
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.
Yes, you can record 4K videos from Galaxy A8 Star's rear camera. From the front camera, you can record up to Full HD videos.