Hi, Khushi.

Neet is an all India common entrance examination for the medical aspirants to get into the undergraduate courses in both government and private colleges. 

every state has 85% of its seats reserved to its own students and rest of the 15% is AIQ which is all India quota. Open state quota is about the 15% all India quota for the admissions. 

No, you can't apply to the other state governments except for your own state or if you're a domicile of the state. You can apply for the all India quota if you're applying for the other state's colleges.

Goodluck