On your cement sidewalk try putting paint thinner directly onto the stain and use a wire brush to scrub it. You may have to reapply more thinner as it evaporates. It may look cleaner than the other concrete but that will go away eventually. As for the siding, just put thinner on a rag and wipe it off. Be sure to test in a spot out of sight to make sure it doesn't take off the house color. It shouldn't but you never know!