What does this rebus puzzle means ?

Which alphabet letter is a question?

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?

A girl was standing near the window thinking something. All of a sudden she decides something and throws something out of the window. She dies very soon after throwing it. She was perfectly healthy and had no disease or allergy. No one killed her and she did not commit suicide.

Can you think of any possible explanation that is logical as well for what happened there?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

In the Thar desert, 3 men found a big 24L Jar is full of water. Since there is a shortage of water so they decided to distribute the water among themselves such that they all have equal amounts of it. But they only have a 13L, a 5L and an 11-litre Jar.

How do they do it?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

If Japan and Panama decided to merge into a single country, probably people will name it Japanama.

Can you think of two more such country's unions that could produce similar names like Japanama by overlapping their three letters?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?