Solution:

The third son bought a candle and a matchstick. He lighted the candle from the matchstick and the light filled the entire room.

Solution:

Ganpat had a black suit and a brown suit.
Harish had a brown suit and a pink suit.
Manoj had a white suit and a black suit.
Tarun had a pink suit and a white suit.

Solution:

step 3 is wrong

Solution:

Playing chess

Game needs two players so Brother-8 is playing chess with Brother-2

Solution:

TIF56

Explanation:
The password is formed as:
T (5th letter of Shruti)
I (5th letter of Arshika)
F(1st letter of Friday)
5(5th day of week)
6(Length of Friday)

Similarly, we will pick the 1st letter for Monday and 3rd letter for Wednesday.

Solution:

Adam and Eve were the only people without navel. As they were not born out of a mother, they never had umbilical cords and thus never had navels.

Solution:

It can be done as shown in the picture below.

Solution:

A Spider

Solution:

They used the planks in the manner that is shown in the figure.

Solution:

A Question

Solution:

Sam : 2
Dean : 5
Castiel : 7

Age diff
7 - 2 = '5' is prime
7 - 5 = '2' is prime
5 - 2 = '3' is prime