Hello,

You have to give your semester exam as specified by the board under which your UG institute is affiliated or if it is a university then it must be conducting the exams by self.

IF you don't give the semester than you will have back papers and you can clear it in next year. You cant clear it in 2nd semester as they are even semester. You can clear odd semester papers in odd semester only.

If you want to give other exams than you have to manage  both else you will lose both.

Better to prepare and attend the exams seriously. Don't miss any exam and give your best that you atleast qualify with a decent mark.

Hope it helps!