Hey there!

It’s a common doubt and confusion for board appearing student.

Accordingly you told that you passed all the 5 main Subjects of your 12 board and failed in optional subject  i.e 6th subject.

if this same is happened so you no need to worry,because you have to pass in only 5 subjects however in your marks sheet the marks of 6th subject will be given which will create a bad impact.

Also i want to mention that for most of boards percentage is calculated by considering top 5 subjects .

However CBSE has no issue with 6th paper as fail and overall you will be passed.

For filling any application you write appeared if having the marksheet of pass in 12th board.

and you are eligible for any other UG course ,but my suggestion is to clear or pass that optional subject .

But if case is different i mean you failed in the 5th optional subject other then the 4 main subject ,then you are appearing for 12th again and not eligible for any other UG course.

hope this will help you

Good luck!