1. Yes, FSP has a lot of charm when you're posted aboard. In Pakistan officers stay is relatively small, and the charm is less I'm afraid. In 30-33 years of career, an officer spends some 20 years aboard. Good protocol is provided when you're abroad, it is no doubt a very respectful job. An officer must be posted aboard to learn different language courses, diplomatic techniques etc etc. But you can not stay only in Pakistan, it's NOT possible and if suppose it is possible then why you're joining FSP? I would suggest you not to join it then.
2. Yes, the promotion is relatively quick. My cousin(FSP, 28th Common) is in 19th grade now. he is probably 39 or 40 years of age. If I'm not wrong FSP has the quickest promotion ratio compared to any department in the civil bureaucracy.
3. Duties of a new CSP in Foreign Office varies from post to post. Most probably you'll be Assistant Director of services, security, or you'll be working at some country's desk. Following are the JOB TITLES/RANKS in Pakistan as well as abroad.
1) Assistant Director(Security, Services, Country Desk)/Section Officer
2) Director
3) Director General
4) Additional Foreign Secretary
5) Foreign Secretary. (BPS 21)
Junior officers begin their diplomatic careers abroad as Third Secretary.
1) Third Secretary or Vice Consul
2) Second Secretary,
3) First Secretary or Consul
4) Counsellor
5) Minister or Consul General
6) Ambassador/High Commissioner/Permanent Representative. (BPS 22, Career diplomats/non-career diplomats).
NOTE: If you're not interested in going aboard and working there then obviously i would suggest you to opt for some other group. Otherwise FSP is very suitable for girls. In order to know about MLCG, please go through my thread in the MLCG section. Also mention your top 5 or 6 department choices, so that I'm able to guide you or suggest you some suitable solutions.