Regarding gmcs

In your case, there is no due date by which you ought to finish your GMCS.

You can opt to do your GMCS any time and kindly bear in mind that it is mandatory to have completed your GMCS in order to apply for Membership of the Institute once your clear your Final Examination.  In other words, you are entitled to take up your GMCS course any time from now on and finish it; so that once you qualify, you can immediately apply for Membership of the Institute.