hey 

yes if your basics are clear from 11th you should now only focus on 12th 

most of the chemistry you do prepares you for NEET as well like inorganic & physical 

organic only 2-3% questions are asked from outside so don’t worry

while doing biology make sure you study it from theory point of view & remember every line you read . solve MCQ side by side

physics- yes obviously you have to do extra hardwork because it’s not very easy but if your basics are clear give test series to assess your physics for competition along side theory for boards

good luck