Prayas, you can appear claim State Quota for 2 States if you are eligible for their States domicile. So there is nothing illegal in it. But if you just been born in UP, you cannot hold their domicile. You have to complete your 10th and 12th in UP to be eligible for their State Domicile. And even if you have lived outside UP, but completed 10th and 12th in UP, then you have to submit the UP domicile certificate to be eligible for UP NEET State Counselling. You can check the complete information at: https://medicine.careers360.com/articles/up-mbbs-admission . But with Delhi, by the virtue of completing all your education in Delhi, you are eligible for Delhi State Counsellig. But as you did mention, if you have legal and valid proofs to claim UP Domicile, then you can absolutely take part in both Delhi and UP State Counsellings.