That workout will not deliver "rock hard abs" by itself. It'll help you get better at doing pushups, which is basically muscular endurance and some strength for your arms and chest, but that's about it. At no point have I ever had "rock hard abs" and I've been a pushup machine at times.

You need to do more than pushups. They activate one set of muscles for one motion. You need to work your legs, your back, your biceps (pulling muscles, which aren't engaged by pushups), your core, etc. Adding resistance work in the form of weights can help as well. All the "special forces workouts" I'm familiar with still have a lot of ab exercises, if that's what you care about, but you also need to engage other parts of your body (hips, thighs, calves, forearms, shoulders, etc) to have a truly healthy body and avoid injuries.

Nope, there is no balance, or completeness, on what so ever in this regime. Where are the exercises for the back and for the lower back, for example.

My advice is to find a good fitness instructor and someone that knows from diets.

It was given to me by a gentleman in the us special forces and I'm a pretty big kid also so I have good genetics for muscle.

I also eat healthy and do cardio