How can i increase my height at the age of 20?

Very unusual: Virtually everyone has fused all of their growth plates by the time they are 20 years old. Once your growth plates are fused, growth is over. Even the very rare person who still has growth potential left at 20, has very limited growth potential before complete fusion, and nothing substantially affects the ultimate height.

Platform shoes: At age 20, there is no way to "grow" taller.The growth centers that determine linear growth close after adolescence, at 16-17 in most females and 18 in most males.After closure, you can not grow taller.