No, this is an external hard drive. Can't use it ask an internal hard drive. Mainly, external hard drive for you to backup data which can transfer from one computer to another computer.
No, this is an external hard drive to be used as a supplemental extension for storing files outside of your computers hard drive. It could certainly be used to store backup files, but it won't operate as your main drive.
Yes, USB external HDD's are very easy. I recommend that you make sure the copy finishes before disconnecting, plus use the eject option when you are done to make sure any open files are closed correctly.