Seeking clarification regarding admission procedure

I got my class 12 result and it's not that good. So I'll be giving improvement exam in one of the subjects. But the result of the improvement exam are scheduled for first week of August. So i won't be able to update my marks in the correction window.

With my old score, I still meet the eligibility criteria for my desired course at DU. So if I score the required marks in cuet. And then fill up my CSAS using my old marksheet marks, can I change or improve my marks with college administration once I get the admission.

If I am not allowed to change my CSAS marks, what impact can it have on my career?

I don't think that I did something that would cancel my admission. It's not fraudulent, ​I had a marksheet, which was officially mine, used it to clear the eligibility criteria and then I wanna "improve" my marks, on the basis of a new marksheet, which is also officially mine.