Can you solve the below tricky visual equation?

Solve the puzzle by telling what does below picture means.

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

I always drive my customer away.

Who am I?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

All of you like to eat me. I am a five-lettered word. Remove the first two and I turn into an infamous animal. Remove just the first and I become a heinous crime. Remove the first and the last and you can groove on me.

Can you guess who am I?