Hello aspirant,

Almost all questions from 11th and 12th class only which you already completed for boards exam.

For  beginners of AIIMS preparation refer NCERT books and also other books.

Solve mock test and have another mock test to check time management and all 

Try to cover important topics initially only and spen more time on it.

And also prepare general apptitude.

My suggestion is to create a schedule for a topic 1 or 2 hours time and overcome the problem and crack the exam.

Hope above information is helpful to you

Thank you