What is the next number in this series?

4,12,84,3612....

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

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

I have no life, but I can die. What am I?

I make two people out of one. What am I?

Why do people go to bed?

A guard is positioned at the one side of the bridge saying ‘A’. His task is to shoot all those who try to leave from ‘A’ to the other side and say ‘B’. He also need to welcome the person who comes from another side ‘B’ to his side ‘A’. The guard comes out of his post every 1 hour and looks down the bridge for any people trying to leave. You are at side ‘A’ and wish to go to another side ‘B’. you also know that it would take 1:45 hr to cross the bridge. How will you cross the bridge?

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

Two prisoners Jack and Jill are locked in a cell.
There is open window approx 40 feet above the ground of the cell.
They are never able to reach there.

Then they plan to escape by a tunnel and they start digging out.
After digging for more than 20 days, Jill comes with the different plan and they escaped.

what was the plan ?

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

O T T F F S S ?