Hii,
Yes, having a backlog in one subject in Class 12 does not mean you have to give up on your dreams, but don't worry, practical options are available to help you move forward without losing an academic year.If you have failed in just one subject, you are usually eligible to appear for the compartment or supplementary examination conducted by the board for which this exam is generally held a few weeks or months after the board results are declared. Once you clear this exam and obtain a passing certificate, you will be considered eligible for further education.
These are some options you can consider
1) Some colleges, especially private universities and institutions, offer provisional admission to students appearing for their compartment exams. In this case, you may be admitted on the condition that you submit your final Class 12 mark sheet after passing the backlog subject.
2) If you have appeared for entrance exams like JEE Main, state-level engineering exams, or university-specific entrance tests, and meet their cutoff, you can still participate in the counselling process. Some colleges allow students with pending results to take part, provided the results are submitted before the final admission deadlines.
3)Many private engineering colleges have flexible admission processes and are willing to admit students who are waiting to clear a single backlog, especially if they perform well in entrance exams or meet other eligibility criteria.

One backlog does not mean your academic journey is over. Focus on preparing for your compartment exam, explore colleges that allow provisional admission, and apply for relevant entrance exams. With proper planning and determination, you can still start your engineering degree this year.

All the best