First of all I welcome you,

You must read out rules and regulations on the front page of this website or dig another source so you will find all your minor answers, by the way. You can sit in CSS exam once you cross age of 21 years with BA 2nd division,

I would suggest you that you have many years to appear in CSS do not become furious thinking that the time is going waste, Complete BBA and the selection of specialized field depend upon your mood toward that subjects.