@mmansoor: It feels a little awkward to me that I give an advice to someone who is more qualified than me but even though I decided to reply to your query because I thought I might help you in deciding your optional subjects.

Why aren't you sure about Computer Science? Believe me, it would help you fetch really good marks as you've done M.Phil in it so it wouldn't be difficult for you to go through the complete course. And it's going to take less time as compared to IR because you won't have to study it from the ground up. But still if you want to opt IR then do opt International Law with it because of an overlapping syllabus between them. Aspirants usually opt Constitutional Law with Pol. Science (Just for your information). Considering group 2, I won't suggest you to pick any subject from it. From group 3, GPP and TPUM are newly added subjects and either one is fine if you manage to find the study material/books but I suggest you to choose either PA and GPP as TPUM looks a bit more technical but decision is yours. I also recommend you to go through the syllabus before opting any subject.

Group 4: Indo Pak History
Group 6: Criminology
Group 7: Psychology/Journalism/Sociology

My recommendations are biased but take your time and decide calmly which optional subjects are suitable for you. Ask for opinions here, go through past papers, go through syllabus, go through threads over here on the forum and then select them, as selection of subjects plays a crucial role in one's success so don't opt in a haste.