Hi Warish

Improvement exams are a way to improve your marks and you can choose more than one subject for improvement exam in the succeeding year. 

Improvement exams are for better performance in exam . You were not able to score expected marks in regular boards exams that's why you are reappearing for improvement exam. 

It depends on your score in improvement exam. You have to work hard and score better to get a good college further.

You'll get a separate marksheet after improvement exam. So, you have to take that marksheet only at the tone of admission .

What is the use off first marksheet when you have improved your marks in second marksheet. 

But for safe side, keep both the marksheets with you because both are valid so you might need both the marksheets at the time of admission . 

All The Best!!