What rules does OS X use for naming mounted volumes?
Yes, this is standard OSX behavior. If you have two identically named volumes, OSX will suffix 2-N with a digit in the filesystem (however, I don't believe they appear differently named on the desktop)
OSX mounts everything under /Volumes/. You can see what the interface is by running the mount command. Physical volumes are mounted in /dev/diskXsY, where X and Y are interface ID's.
¯\_(ツ)_/¯ - you asked it in the Apple area.