1. Is it allright to pay using someone else's credit card?
Not sure about that. I recall reading something about that in the forum a few months back where someone used a friend's card. You could do a search and confirm. Also the guidlines dont specifically forbid it.
2. Is PF (Provident Fund) counted in past earnings? (From India)
I dont think there is a straight forward answer to that. Ordinarily I would say that since it is your employer's contribution and it comes outside of your gross salary, it should not count towards past earnings. On the other hand, I have seen a couple of companies that apply CTC (Cost to Company) in a convienent manner where they bump up your gross and extract ESI (Employer's Contribution) from it. In those circumstances I would include my full Gross without worrying about the different components that constitute it. There is also an optional (or minimum) contribution by the employee that obviously comes from your pocket.
My advise, just stick to your gross salary. Anything outside it, and you will struggle to get points for it.