it's up to you. you need to understand that HGH and steroids are two different things that work in different ways!
of course, the diet (calorie deficit with proper macro balance) is the number one thing you should focus on when it comes to stripping body fat around ab region. the second thing you should pay attention to is increasing the activity level. but yeah, HGH itself has been proven by many studies to help aid the fat burning around the ab region. Steroids, clenbuterol, and numerous others can help, but remember that the more compounds you use (and the higher their dosage), the higher the risk of side effects.
that's possible as long as you have a perfect diet, workout plan, and rest enough.