Is it true that we can increase our height at age of 20 ?

I guess No. At that age, you are beginning to slow down the hormones to keep you growing and maintain the maximum height a person you can have, it may be increase in some sort of medical procedure, or medication, it depends on your life style and eating habits. When you eat to much although you are growing tall, the tendency it barrens up with your tummy, so you look stout. But when you are energetic, especially keep on jumping routine, you will come into a point of being tall, but don't do it when your tummy is full, or after a meal. If you eat veggies, as old does, helps you to increase that height, but it is more effective during infancy until it reaches 18. Its not how tall you are, not unless you are aspiring candidate for a basketball team or be the tallest person. Some say hereditary, when your olds are tall surely they will transfer the genetics into your body, but when nobody is taller than they are, you have to accept that this is the farthest you can have. Increase you knowledge and you will go far, as if you are the tallest man on earth.