To capture an image of the screen, press "home" and the power button at the same time. The "Gallery" app shows screen images as a separate collection.
The user manual explains how to save an image for a contact icon, but it does not mention that contacts stored on the SIM card cannot have icons.
The user manual says that when the phone is powered down, you should hold the power button down until the Samsung logo appears. That time seems to vary, but you actually only have to hold the button down 6.5 seconds.