Hi Khandakar,

Firstly understand that proforma a1 and a2 are documentary declarations of your proof of residence for a significant period of time at a particular place so as to get the eligibility status of a domicile candidate for a particular regional entrance examination. These documents are signed and approved by the principal of the school from where you completed class XII and by a government official so as to attest your domicile status. 

Thus, both proforma a1 and a2 are needed at the reporting centers as they certify that you are a resident of the region that falls under that regional entrance examination.

BEST WISHES!