Yes, you please frequently visit the website of National Open School.  If you are residing in Delhi try to visit NOS office.  Dont forget to keep ready your class X and other certificates.  After the registration, there are also weekend classes arranged by NOS in the near by schools. 

Yes definitely you can take admission to class 12th under National Institute of open schooling that is NIOS and complete your rest of the school in that is close to us so there is no problem you need to just register for NIOS class 12th and complete the 12th examination by appearing for the exam.