What does the below image rebus riddle means ?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

What time is it when an elephant sits on a fence?

A man walked into a pub and went straight towards the Barman. He asked for a dirty martini from the Barman. The Barman thought something and then pulled out a pistol from his drawer and aimed it directly at the man. Why did he do that?

A convention is held where all the big logicians are summoned. The master places a band on everyone's forehead. Now all of them can see others bands but can't see his own. Then they are told that there are different colours of bands. All the logicians sit in circle and they are further explained that a bell will ring at regular intervals. The moment when a logician knew the colour of band on his forehead, he will leave at the next bell. If anyone leaves at the wrong bell, he will be disqualified.

The master assures the logicians that the puzzle will not be impossible for anyone of them. How will the logicians manage ?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

How many sides does a circle have?