Revalidation of ca final registration

Hello Sir/Ma'am/Friends,

This is to mention that I had registered for my CA Final (old course) on 18th of February, 2013. Therefore, it is understandable that the validity of my CA final registration period (which is 5 years) is going to expire on 17th February 2018. I have appeared for CA Final - Group 1 in November 2017 and awaiting the result. I have not yet cleared my Group 2 and willing to appear this or Group 1 or both Groups on May 2018. I think that most probably I have to mention the details of revalidation of Final registration in the exam form if such is applicable to me then.Therefore, can anyone please let me know what shall be the ideal time for me to file revalidation form to the ICAI so as to extend my CA Final Registration period (old course)? And, if I revalidate, shall I remain in the old course or I shall be registered to the new course by the ICAI? Please reply, thanks in advance.