Correct answer is 2. Explain why 4 is more stable than 5 and 1 more stable than 3

Q 9. In the given compound
 

The correct order of reactivity of H atoms towards free radical substitution is

(1) 2 > 4 > 6 > 5 > 3 > 1
(2) 2 > 4 > 5 > 6 > 1 > 3
(3) 1 > 4 > 2 > 5 > 6 > 3
(4) 3 > 1 > 5 > 6 > 4 > 2