1. It is an alternative but you don't need it to play WSR through USB.
2. Not recommended to install rev13B, it outdated and not needed.
3. You can play WSR from USB.
4. Save files, Mii's, and Channels are saved onto the Wii internal memory NOT the hard drive.To load the game from a USB drive, boot up the game from a disc and create a save file. Then USB loading will work like normal (make sure the 002 fix is enabled on your loader)