According to the Boeing web site:

"The KC/C-135 series was initially designated within The Boeing Company as the model 717. In January 1998, the 717 model number was reassigned to the commercial line for the 717-200 regional jetliner."

The KC/C-135, among other things, have a crew entry hatch aft and below the cockpit instead of the standard entry door. Also, the military version actually came ahead of the commercial 707.

As for the MD-11 sans landing gear, it may simply be sitting on jacks. Sometimes aircraft are jacked up to test or install landing gear, but I don't know if it applies to "heavies" such as the MD-11.