1. No, any of the regional languages i.e Punjabi, Pashto, Sindhi, Balochi can not be opted with Urdu.
2. So, Punjabi would not be a combo. with Urdu.
3. It is a fact that regional languages are always high scoring provided if the candidate somewhat fulfills the demands of that particular language. If one thinks that one will be saved just due to the high scoring trend of any subject, that is just misconception.
4. Yes, Punjabi can also be opted for CE-2015 without getting any fear about 2014 paper. The underlying fact is the exam is getting change. So selective study won't work better. If you go through Punjabi syllabus, do just with the language even in smaller period, you can still fetch high scores in this subject.

Regarding your second query, it is simple that you can not take Punjabi with Urdu. So you will not be able to replace Int'. Relations with Punjabi. To me, Int'l Relations would be a moderate scoring subject and Punjabi comparatively more scoring one provided if you attempt the Punjabi paper judiciously..
Hope you got the point.

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"But screw your courage to the sticking place,
And we'll not fail." _Shakespeare, 'Macbeth')