Drinking a lot of milk throughout your teenage years and sleeping consistently 8-10 hours a night can help a person gain a few more inches of height then they normally would.
It's not that simple. You gain height when you gain height not when you eat spaghetti or rye bread.
Hanging from a bar will only temporarily cause a slight gain in height.
no after age 21 the height is not increased.
No.
by the age of 21, you have fully grown.
No.
Yes
At 20 years now, you might not gain any further height.
never
Your height will be mostly a matter of the Genes you inherited and your diet. Not much other than staying healthy that you can do about that.
No. In principal the compression on the leg joints will "slightly" decrease your height. However this will be compensated during the night, when you will actually gain height.
streach ball