if Answer is 64 and i filled 0064 will i get marks in jee main

0064 and 64 are the same thing except some null digit ahead. There is a 50-50 possibility depending on the way the exam answer verification is designed. If it can judge the similarity you will get marks but if it doesn't judge the similarity and is programmed for the same to same answer then you will not get answer. So this kind of things have no answers except for hoping the best.

**If its mentioned or anyhow intuitive to put a four digit value then also you have a good possibility of getting marks.

I hope this answer helps. All the very best for your future endeavors!