"and she shall remove his shoe": This tells me only of his shoe (i.e., a shoe that he owns). Whence do I derive (that chalitzah is valid with) anyone's shoe? From (the repetition of) "shoe" (here), "shoe" (verse 10) — in any event. If so, why is it written "and she shall remove his shoe"? To exclude as valid for chalitzah (a shoe) so large that he cannot walk in it or one so small that it does not cover most of his foot, or one that lacks a heel.
"from his foot": From here they ruled: (If she removed the shoe) from the knee-joint down (in the case of one whose foot was amputated), the chalitzah is valid. "his foot": It is written here "his foot," and elsewhere (Vayikra 14:18). Just as there the right (foot is specifically indicated), here, too, the right (foot is intended).