Dear Student, The Certificate no.3 given in the Brochure of UPSEE is a Proforma For Certificate Of Domicile of Uttar Pradesh, This is advisable that you should fill that form which proves that you are a permanent resident of Uttar Pradesh and get it attested by respective authorities.

The Domicile Certificate issued by State Government is also used for the same purpose but The validity of that domicile certificate  is of 3 years and after the tenure of 3 years you need to renew it. So that's why UPSEE has given that certificate in the Brochure which proves that you are a Current Permanent resident of U.P.

However if your Old Certificate is also latest than it will also work but this is advisable you should also fill the Certificate No.3 So you don't need to worry about anything at the last moment.

All the Best!