Yes, you are eligible to appear for NEET. Even though you got 42% aggregate in PCB under the general category, since you have a valid OBC caste certificate from Uttar Pradesh, you will be considered under the OBC category. For OBC and other reserved categories, the minimum eligibility requirement is 40% aggregate in Physics, Chemistry, and Biology in 12th board exams. So with 42%, you meet the criteria and can apply for NEET under the OBC category.