Dual screen/USB formatting on Linux

I was using Linux (Mint) on my old laptop for a while, and two things were annoying me a bit:

• when I was using dual screen mode (connected an external screen to my laptop), I couldn't turn off just a laptop screen so that I can watch a movie on another;
• I installed a Mint instance from a USB drive, but then in Linux I couldn't format it so it works like a "normal" USB drive; had to use Windows.

I'm thinking of coming back to the system, and in regards to the above points, was it something I was doing wrong, or is Linux not offering those functions?