Dear student,

Yes, you have to fill the Certificate no.3 given in the Brochure of UPSEE as it 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.

Hope it Helps!