Answer: (2) > (1) > (3) > (4)
Step-by-step explanation:
(1) a +1 charge and a -1 charge separated by 200 pm:
The potential energy in this case will be,

(2) a +1 charge and a +1 charge separated by 100 pm:
The potential energy in this case will be,

(3) a +1 charge and a -1 charge separated by 100 pm:
The potential energy in this case will be,

(4) a +2 charge and a -1 charge separated by 100 pm:
The potential energy in this case will be,

So, the order from highest potential energy to lowest potential energy is:
(2) > (1) > (3) > (4)