I am writing this answer from my personal experience.
From which year during MBBS should you start preparing for NEET PG ? The answer is NONE.
HERE IT IS WHY :
Till you come to the final year, whatever you have studied you will very easily forget. Consider that you have really good memory and you do not forget what you have read in previous years, my dear all of whatever you have read gets updated/changed.
Anatomy : An artery stays as an artery, A muscle remains as muscle but the course of nerve changes in skull as per the current research going on. 3 layers in embryology ectoderm mesoderm endoderm. Now there is 4th layer : Neural Crest Cells.
MCQ are asked from the Neural Crest Cells.