какие мышцы пресса дают кубики ???боковые, верхние, нижние или какие ещё там есть???

You need to work out regularly on each abdominal separately. Assuming that you want to get a 6-pack, you need to divide them into 3, so make it 2 abs a day. Do 3 rounds of 30-40 sit-ups a day.
The most important part of the rectus abdominal workout is diet. If you have high body fat, and fat stored around your abs, you need to get rid of it because no matter how big the muscles are, they will never be visible underneath all that fat.
When you work out, you need to do it regularly but you also need to give the muscles a rest so that they could build up. An important aspect of this is to eat properly. For that you will need to eat food with lots of protein but that contain low amount of fat, such as: 1) Chicken 2) Fish 3) Eggs (though they have a lot of fat and calories) and green beans.
You could also consider getting whey protein (make sure it's 100% natural). It helps with burning off the calories, and also helps you build lean muscle with better definition.
So to summarize: Regular exercise (abdominal training with cardio), food and resting.

...я тоже в молодости когда-то занимался спортом и прессом тоже... .
....вот наверное поэтому на меня до сих пор ещё обращают внимание и некоторые дамы... .
....успехов и удачи тебе, мой юный друг... .
...терпения и труд - вот главное достижение успеха в любом деле... .
... С Новым Годом !!!

Чудес на свете не бывает! Вы сами правильно ответили на свой вопрос и всё прекрасно понимаете! Попробуйте качать пресс (хотя бы верхние подъёмы) с весом от 5 кг на груди + диета, диета и ещё раз диета! Удачи!