Hey there,

If you appear for the improvement examination then you will have to give the jee advanced examination again to get the seat through this examination. I will suggest you to continue preparing for the jee examination next year also. 

I hope you have got the answer.

Good luck ahead !

Hey Sanket, Yes you can take admission on basis of your previous  JEE MARKS. You will be giving improvement exam this year means in the year of passing Class 12 only then you can evaluate your that marks and can get a good seat in IIT, NIT and even for IIIT.