Hello Student

No it is not possible for you to appear for improvement exam after 5 years of getting your result of class 11&12 with low percentage. Take admission  in open schooling system or in regular schooling system for  repeat exam. If you pass 12 standard examination from National Institute of Open School system then you will also be eligible for appearing NEET UG exam because National Institute of Open School system is under the supervision of Education Ministry Government of India. If you not want to appear inrepeat exam then he have to appear this repeat exam as a private candidate.  Your result must be a good  that will be very easy for you to appear for any kind of examination or entrance tests.

This helps.