I don't really think this is a good idea personally... Strength training can put a lot of strain on the heart. At your age this shouldn't be a HUGE problem, but for the sake of having a system that can properly handle it, you should be doing cardio as well.
Truth is, you should be working everything, not just what you want to look good. Your body has weird ways of changing, and when you focus all your exercise into one area you can get really weird bulky areas.
"Pecks" are always a nice novelty, but the fact is, if you don't have the entire body to go with them, they just kinda look like mini man boobs.
Also, if your ENTIRE body is healthier, not just the muscles in your chest and arms, then the recovery your muscles do will be faster and more thorough giving you more effective results from your workout.
And yes, it's true, all your muscle gain happens during recovery. When you exercise your muscles get tiny hairline tears in them. As these tears heal over, the muscle builds larger and stronger. Your muscles may in fact bulge after a workout. This isn't built muscle, it's basically swelling because your muscles have been slightly damaged. But damage is all part of the building process.
That's all I have to share. I just disagree with your whole idea of "I want this and this to look good". I don't think it's a healthy way to exercise, or the right reason to start exercising. Bessides, when people see it, and the rest of you, they're going to know you spent all your time building those muscles just so they'll look good. You wont exactly fool people into thinking you're that strong or in great shape or anything. You'll just look like this unfit guy with carved arms and little perky lumps under his shirt. The rest of your body, and even how you carry yourself wont be the same as someone who's in shape though and you wont be properly distributed. It'll look awkward IMO.
As far as your abs go, lie on your back, hands behind your head like you're going to do a situp. Instead of sitting all the way up, simply lift your shoulders off the ground. This will still work your abs, but wont put any strain on your lower back. They also make devices that assist in situps to help reduce the tension on the back and neck. I don't know what they're called, but they're like bars that roll with you, I'm sure someone here knows what I'm talking about...
Your abdominals are probably one of the most important parts of your body to exercise. They're a very strong and large group of muscles, so don't be afraid to push yourself.
One way or the other though, without exercising your entire body, you will not feel as strong as any part of you may look on the outside, so you really are just building an unnatural and bizarre body build purely for the sake of aesthetics.