You just can't plan for these things for JEE advance. You don't know for how much paper will be asked, you don't know the particular subject weightage, you don't know whether it will be difficult like hell as in 2016 or it will be a cakewalk like in 2017.

So, there is only one thing which you can do, i.e prepare each and every subject honestly and with equal proportion.

All the best!!!

Hi

Yes it is possible to clear of course, considering you do have a basic knowledge of the third subject too. A minimum cut off marks (generally 30% for general candidates) for each subject is set by the organizing institute. If one fails to clear this cut-off in each subject, the candidate's name is not even included in the rank list .