Max Shutter speed
Sony A7R III can shoot continuously at max speed of
10.0 fps and has max shutter speed of
1/8000 sec.
Flash
Unfortunately A7R III doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Focusing
Sony A7R III features both Contrast Detection and Phase Detection autofocus (AF) systems which ensures speed and accuracy of focusing in most situations. The AF system has 425 points to choose from. Sony A7R III also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically. In addition to the face detect AF, A7R III has a more sophisticated feature called
Eye Tracking AF which detects and locks focus to the selected eye of the person in the frame accurately and tracks as the subject moves. Eye tracking AF of Sony A7R III is a perfect feature for shooting portraits and is especially useful when fast lenses are used and the depth of field is very narrow.