Questions

The letter 'E'.

As of the above given data,

It is in the 1st place in Earth, 2nd in Heaven and in the middle of the Sea.

It appears once in a Year and twice in a Week.

It is present in February, June, September, October, November & December.

But not in the Month.

Hence, it is the letter 'E'.

The inside of the bulb being a vacuum, the outside air rushes in when the bulb is broken. The vibrations of the rushing air molecules produce the sound.

From the hints,

Only two options for 1st and 2nd digits => 4,2 and 9,3 since it is single digits

Sum of second and third digit  = 10 

If 2 => 3rd digit = 8

If 3 => 3rd digit = 7

4th digit = 2nd digit + 1 => (2+1 =3) or (3+1 = 4)

Sum of all digits = 30

Let 5th digit be x

=> 1st possibility = 4 + 2 + 8 + 3 + x = 30 => x = 13 (Not possible since it has 2 digits)

=> 2nd possibility = 9 + 3 + 7 + 4 + x = 30 => x = 7

Therefore, the PIN is 93747