yes you can it played all types of files wmv, mp4, avi, DivX, mpg, flv from a 1tb Hard Drive that I plugged into the TV. flash drives works as well also. just plug into the usb port directly had no difficulties whatsoever.
Definitely yes...we put my camera USB and cord and they both worked great and installed a HD portable WD and ran videos and movies and everything came up crystal clear. The picture on this TV is incredible, really beautiful.
I believe you can as long as the content is formatted so that a player built-in to the device can read the file. Otherwise, you can import the file into iTunes, and then connect your iPhone or iPad to the Samsung using an adapter and play the content