What does this rebus riddle means ?

When monkey rotate the gear, which mark will be hit 1 or 2 ?

What can you hold in your right hand, but never in your left hand?

The cream is heavier than Milk. True or False?

What is so fragile that saying its name breaks it?

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

I drive at an average speed of 30 miles per hour to the railroad station each morning and catch my train. On a particular morning, there was a lot of traffic and at the halfway point, I had averaged only 15 miles per hour. How fast must I drive for the rest of the way to catch my train?

How many Watermelons are there in the below picture?

What does does this rebus picture means ?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?