Looks to me as if Putin is on steroids for some illness. He has a a classic steroid puffy face.
I understand that Novichok decays to nothing after a week or two. That is why the body is being withheld and, of course, if the body is stored in a mortuary whose cooling system has, unfortunately, broken down, the body will have decayed too much for signs of violence to be recogniseable.
Actually, if the Russians, or rather Putin had any sense, he would simply have had him cremated and returned the ashes to his wife, claiming that as she lives outside Russia, this was the easiest and kindness way to reunite her quickly with her deceased husband.