If I start preparing from now, which chapters you recommend me to focus of PCM to get good AIR?

I would suggest you to devote your time as per the weightage of topics -

Maths - Inverse Trigonometric Functions Weightage: 2% Circles and Family of Circles Weightage: 6% Sequence and Series Weightage: 5% Applications of Derivative Weightage: 4% Limit and Continuity Weightage: 3% Matrices and Determinants Weightage: 4% Straight Lines and Pair of Straight Lines Weightage: 2% 3-D Geometry Weightage: 5% Probability and Statistics Weightage: 7% Vector Algebra Weightage: 5% Integration Weightage: 8% (Definite + Indefinite integration) Complex Numbers Weightage: 5% Parabola Weightage: 3% Trigonometric Ratios Weightage: 3% Logarithms Weightage: 1% Quadratic Equations Theory of Equations Weightage: 5% Sets, Relations and Functions Weightage: 4% Differentiation 2% Permutation and Combination Weightage: 2%. You should study this properly as concepts from this section will be needed in Probabilty Binomial Theorem Weightage: 1% Locus Hyperbola Weightage: 2% Ellipse Weightage: 2% Fundamentals of Mathematics Solution of Triangle 1%

Chemistry - General Organic Chemistry 9% Alcohol Phenol Ether 7% Redox reactions 6% Chemical Bonding 5% Coordination Compound 5% P-Block Elements 5% S-Block Elements 5% Aldehyde Ketone 5% Solutions 5% Solid State 5% Chemical Thermodynamics 5% Ionic Equilibrium 3% Chemical Equilibrium 3% Surface Chemistry 3% Atomic Structure 2% Gaseous State 2% Transition Elements 2% Polymers 2% Nuclear Chemistry 2% Chemical Kinetics 2% Mole Concepts 2% Amines and Diazonium Salts 2% Biomolecules 2% Alkanes, Alkenes and Alkynes 2% Electrochemistry 2%

Physics - Units and Dimensions Weightage: 2% Measurement of Errors Weightage: 2% Vectors Kinematics Weightage: 1% Newtons Laws of Motion Weightage: 4% Friction Work, Energy and Power Weightage: 5% Electrostatics Weightage: 6% Current Electricity Weightage: 7% Wave Optics Weightage: 5% Ray Optics Weightage: 6% Centre of Mass, Momentum and Collision Weightage: 5% Rotational Dynamics Weightage: 4% Simple Harmonic Motion Weightage: 5% Fluid Mechanics Weightage: 2 5%. Wave Motion and String Waves Weightage: 5% Magnetism Weightage: 6% Heat & Thermodynamics Weightage: 6%.Nuclear Physics Weightage: 5% Modern Physics Weightage: 5%, Circular Motion Weightage: 1% Gravitation Weightage: 1% Properties of Matter, Elasticity Weightage: 2% Sound Waves Electromagnetic Induction Weightage: 3% Alternating Current Weightage: 1% Semiconductors and Electronic Devices 5%.

Good Luck!!