hello,

You have the syllabus of NCERT for physics,maths and chemistry. There is no important part as question paper is unpredictable and  no one knows how many question will come from one chapter. If you have any JEE main preparation book or an previous year paper collection book then you can see analysis for every year. They do this to make the students know how many questions are asked from each chapter. but this doesn't says that the chapter from where most questions came previous year will come this time too.

No, it won't happen. The papersetters of jee main board are enough intelligent and they know how candidates think which is why it is one of the toughest exam across in India. The reason is paper is unpredictable and no one knows what will be asked. Paper is not that difficult but it will easy for those students who have given most of their times for practice and learned it. if a candidate gets confused then answer will get wrong which says that the practice level is low.

Practice is the only key which will help you crack the exam. For now you don't have enough time so just learn the topics which you find easy for you and numericals of those chapters. In the meanwhile solve previous 5-6 year Jee main papers too.

Hope it helps!