You are completely mistaken.
For the conditions you listed (as well as the guy who grew to 7 feet tall you mentioned earlier), doctors are using CORTICO-STEROIDS, not anabolic steroids. Cortico steroids are a totally different class of steroids, and they infact break down and destroy muscle tissue.
Yes, anabolic steroids for the most part can fuse growth plates closed if you are not done growing yet. It is actually the result of estrogen aromatization that does this, but if you use aromatizable anabolic steroids in supraphysiological levels, it does do this.