I think a <200lb bipedal 2-arm robot which could box would be a marvel to see, but if there aren't any rules which say how many arms and legs the combatant has to have, the robot is gonna have wheels, most of its mass in the lower body so as to make it un-topplable, be made of some lightweight metal, and have an arm that plays chess and a boxing glove on an actuator that can break concrete.
And on the point of existing rules, the existing rules aren't enough for this type of competition. First of all the weight class: are robots men or women? It says age 17+, how does that affect the robot? There's no rule against pouring water on the robot, but there also isn't a rule against releasing nerve gas. My robot is a pourous metal box with a canister of gas which renders everyone unconscious, do I win by K/O?
Also, they already have battle robots, and they look nothing like conventional humans (one common design is a flat panel that slides under the opponent and jettisons them)
As for reaction speed of man (100+ms vs machine), I'll just link this: https://www.youtube.com/watch?v=3nxjjztQKtY