Spot what is wrong here in below Picture?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

What jumps when it walks and sits when it stands?

A boy was at a carnival and went to a booth where a man said to the boy, "If I write your exact weight on this piece of paper then you have to give me $50, but if I cannot, I will pay you $50." The boy looked around and saw no scale so he agrees, thinking no matter what the carny writes he'll just say he weighs more or less. In the end the boy ended up paying the man $50. How did the man win the bet?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

While handling a project, the landscaper is asked by the owner of the mansion that he wants four trees in front of his mansion that are exactly equidistant from each other.

How will he do it?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?