Dear Gauri, giving only 12th Board exams from Delhi doesn't confirm you the benefit of 85% State Quota. This is because during the document verification you have to provide address proof that you are resident of Delhi. So the two conditions -

• Passing 12th from Delhi 
• Address proof of Delhi

can provide you with benefit of 85% State Quota. Or if you can provide the domicile of Delhi then there will be no need of address proof. It is really difficult to get the domicile of Delhi as you already have the domicile of UP.

All the best

Hope this helps