See in 12th you have Electromagnetic theory and for that many times the questions are linked up with mechanical problems such as a Pendulum in Electric Field etc. SO if you wish to study, then you are recommended to complete the following topics first:

• Vector
• Circular Motion
• Simple Harmonic Motion
• Newtons laws of motion
• Work & Energy

This subjects, may have direct link to your 12th subjects. So do study them.

For the NEET chapterwise weightage you can consider the link below:

https://medicine.careers360.com/articles/neet-chapter-wise-weightage-and-important-topics

I hope this helps. Wish you a great day!