hi,

see jee main and jee main syllabus is same as 10+2 course, however the questions level is bit difficult and you need to give extra hours of studies to learn techniques to solve and quickly answer the questions. however I would suggest you to first complete the 11th syllabus and then start jee main questions, see to solve jee main question it is necessary to know the basic things , so when your 50% syllabus of 11th will complete you can start solving jee main questions.

you may follow arihant or tata macgraw books for practicing.