Some of the basic chapter which if not done can create problems for rest of the chapter in Physics and Chemistry are as follows:

Physics:
Laws of Motion
Kinematics
Work Power and Energy
Oscillations and Waves
Electricity
Magnetism
Optics
Modern Physics

Chemistry:
Mole Concept
Structure of Atom (coincides with modern physics)
Chemical Bonding
General Organic Chemistry

These chapter are at the heart of NEET and should be completed anyhow before appearing for the exam as these can make or break your rank.

Hope I have answered your question. All the best!