What does does this rebus picture means ?

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?

If Rajina's daughter is my daughter's mom, who am I to Rajina?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

Look at the picture and find out which square is not linked with any of the other squares.

Replace the letters of words with a number so that the below equation holds true

BASE +
BALL
---------
GAMES
----------

Can you find out which options fits best with the missing column?