First constitutes the second. As combining 'Atom' we get 'molecule' in the same way combining 'Cell' we get Organism' .

All are the colours of rainbow.

As, 25 is common in both 25 and 625 and 6 is added.
Similarly, 35 is common in both 35 and 635 and 6 added.

In word GREAT , the number of alphabet = 5
? GREAT = (5)² = 25

All are the Capitals of Indian States.

All are the currencies of different Countries.

As, Peacock is the National Bird of India Similarly, Bear is the National Animal of Russia.

63/3 = 21
27/3 = 9

100 = 10² : 121 = 11²
144 = 12² : 13² = 169

(08)² + 2 = 66
(06)² + 2 = 38