Can you find the missing piece of the Porsche?

I am 5 letters long.
My first two tell you who I am
My first 3 could be a medicine
My last three reversed could be a young boy.
My 4th, 3rd and 2nd in that order could be a fruit drink.
If you have me you may hang me round your neck
WHAT AM I ?

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 10 matches are played in total, how many players participated?
(b) If 20 players took part in the tournament, how many matches were played?

John was so frustrated to be the suspect of being a sleeper terrorist that he shoot himself right between the eyes with a revolver in his toilet. The revolver and the bullets were accurate. Minutes later John walks out of the toilet unharmed.
How can this be possible?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

What can you see in the middle of March and April that you can never see in any other month?

Find the next number in the sequence

5 12 24 36 ?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

If eleven plus two equals one, what does nine plus five equal?