What is always in front of you but can’t be seen?

What is the word or phrase?

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

How could a baby fall out of a twenty-story building onto the ground and live?

You can see it everyday, But cannot touch it at will. What is it?

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

Can you find the largest Three-digit number whose sum is 14 and whose square is less than 5,00,000?