Do we have to separately apply for each B school (which we aim for) before giving cat , snap , nmat exams?( Apply date is given before cat)

Apply seperately for CAT Allied colleges. Check their websites for the application deadline. And yes, you'll have to pay the fees before the CAT results if required.
Regards,
Mrudul Naik

No. The entrance exam like CAT, SNAP and NMAT by GMAC are centralised exam systems. CAT is a centralised application system for all IIMs and as you apply for CAT, your application is automatically made to all IIMs. Thus, by applying to CAT, candidature for all IIMs is assured. Other institutions selecting canddiates basis CAT scores require fresh applications separately.

In case of Symbisis Group of institution (about 15 institution), applicants require to select the number of programmes  while filling SNAP form and accordingly pay fee at the time of filling SNAP itself. For NMIMS also, you first need to apply for NMAT by GMAC and thereafter apply separately for NMIMS. in Case of NMAT by GMAC, there are mnay other institutions which accpet score of the exam for shortlisting. But for this, canddiates need to first apply separately with NMAT by GMAC scores.