Hi Abdul Rauf...I faced this dilemma too being an engineer. I qualified CSS in 2018 and have unfortunately given PAS as first re, PCS as 2nd and FSP as third due to my father's wishes. I now regret my choice.
However, I see that you too have made it to PAS. How are you liking PAS given that you wanted FSP? Are you satisfied? Why did you not keep FSP on 1..?