What do you answer even though it never asks you questions?

I live in a bowl. I can swim. I have a tail. I also have fins and big eyes. What am I?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

John: "Hi Teacher, What is your favourite movie ?".
Chemistry Teacher: "Indium Cerium Platinum Iodine Oxygen Nitrogen".
Ten seconds later... John replied I got it.

Do you?

My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years ?

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

What does man love more than life, and hate more than death or mortal strife; that which satisfied men want; the poor have, and the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?