Here are the three tasks, completed.
The first one is a continuation of the previous leg rig, now with a spine and head.
The second task is another rig, this time for a mechanical leg with piston. The geometry is parented to the joints, so it actually moves with the skeleton rig.
Here is an X ray view with skeleton underneath.
The third task was another walk cycle animation. Where as the first walk cycle is supposed to be generic. This has a slightly different characteristic.