3 months GMCS compulsory or Optional?

The new GMCS 3 months residential programme introduced by ICAI is making a lot of confusion among CA final students. Even they are charging huge fee of Rs 48000 as it is Rs.4000 in case of Old GMCS. Is it mandatory to purse 3 months residential programme or can we have option to choose between OLD GMCS (15 days) and this new GMCS (3 months). Is 2 years of practical training enough to apply for GMCS or is clearing CA Final mandatory?