What does below chemistry rebus means?

Christina is older than Kareena and Karishma. Katrina is older than Karishma and younger than Kareena. If Kareena has a brother named John, who is older than Christina, who's the youngest?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Decode the below four famous ciphers:

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

A few friends are enjoying their sea voyage in a boat full of apples. On the way, they felt hungry and thus decided to eat the apples. Together, they ate two dozen of apples. When they have eaten the apples, will there be any change in the water level?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

An evil man kidnapped someone and made them take one of two pills. One was harmless, but the other was poisonous. Whichever pill the victim took, the kidnapper took the other one. The victim took their pill with water and died. The kidnapper survived. How did the kidnapper get the harmless pill?

What do you call a fish without an eye?

What will you call your mother's brother's brother-in-law?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?