Hii Anshul..

With the rank like 4 lakh in jee main it's not possible to get any core branches in good colleges.Or you get 4 ranked / 5 ranked government colleges through reap.

But there other colleges which took admission on the basis of both  class 12 marks  and jee main score,but as your 12 percentage are not that much good ,I am suggesting you to took admission in any private college in Rajasthan .

And if you really want to get in nits or iit in cs branch ,you may drop a year , prepare for jee main And also prepare for improvement as 75% are requirement.

Hope it help ..