There was a strange boy who was born before his father. How can this be possible?

Can anyone tell me a word in the English dictionary which has a silent 'z'?

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

My first is in chocolate but not in ham. My second is in cake and also in jam. My third at tea time is easily found. Altogether, this is a friend who is often around. What is it?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

Pronounced as 1 letter, And written with 3, 2 letters there are, and 2 only in me. I’m double, I’m single, I’m black blue and grey, I’m read from both ends, and the same either way. What am I?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

What do the following words have in common?

Assess
Banana
Dresser
Grammar
Potato
Revive
Uneven
Voodoo

I can write cow in 13 letters.

Can You?