1. Let G be a group of order 4. Prove that every element of G has order 1,2, or 4.

2. Classify groups of order 4 by considering the following two cases:

a. G contains an element of order 4

b. Every element of G has order <4

could anyone please help me to solve these problems?

and what does it mean by 'Classify groups of order 4'?