I gained a lot of muscle on my torso/upper body on T and it helped to further define my legs which were already muscular. Prior to getting HRT I was working out diligently, lifting weights, for about 2, nearly 3 years. When I started HRT I was not able to work out (I was recovering from surgery) but I packed on a lot of muscle anyway. I did not restrict my food other than avoiding junk and eating a good balance of protein with healthy carbs and fats, and I gained a lot of muscle weight. So, the T will help a lot but you still need to exercise and eat properly to condition your body.
If you want abs, do bicycle crunches to tone them up and make sure your body fat is low enough to show 'em off.