Can you fill the blank with the correct number?

6 30 870 756030 _____

What you cannot hold but it is yours?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Who has married many women but was never married?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

A man desired to get into his work building, however he had forgotten his code.
However, he did recollect five pieces of information
* Fifth number + Third number = 14
* The fourth number is one more than the second number.
* The first number is one less than twice the second number.
* The second number and the third number equals 10.
* The sum of all five numbers is 30.

What is the code ?

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

A man dies of old age on his 25 birthday. How is this possible?

Can you write down eight eights so that they add up to one thousand?

I am a five-letter word and comprises two different vowels and three same consonants. I am so strong that I can spoil your entire work.

Can you find out who am I?