Start with biology. Secure 360 marks first. And solve as many papers, test, whatever you can. Time is precious okay?. Study regularly for 7 8 hrs per day you have to give this much atleast because time is less and you have to secure good marks and this year competition is also very high..
In biology start with human physiology then genetics then reproduction then ecology and soo on.. remember from last 3 4 years 15 to 16 questions are asked from human health this one chapter have alot of weightage so start preparing without wasting your time..
In chem start with physical because numericals will never ditch you and some important chapters are:-
Physical:- chemical equilibrium, chemical kinematics, surface chemistry, solution and colligative properties
Inorganic:- chemical bonding, coordination compound, d and f block, p and s block
Organic:- carbonyl compound ( most of the naming reaction will be asked from this), GOC , alkyl halide, alcohol and ether, IUPAC and isomerism
In physics mechanical physics have high weightage but you dont have much time you can go for part 2 of 11th and 12th as it is easy and scoring!!