Hello aspirant,

YES, you can repeat the class 12th and can give your JEE mains and advance examination. There are many students who take a year drop to prepare for JEE. You're allowed to write the JEE mains exam 3 times i.e 3 attempts. Many students persuing their engineering also write mains again.

Every candidate is allowed to give JEE mains 3 times and JEE advance 2 times in a consecutive year from the year of passing from class 12th.

Further, below are some of the best preparation tips and strategy that you can follow for yoru JEE mains and JEE advance examination :

Prepare A Well-laid Plan

Draft a daily schedule.

Prioritize the topics that require more time and relevant to the subject.

Stick to the routine and pay special attention to problems.

Get Hold Of The Syllabus

Manage your time effectively

Understand Basic Concepts

Before delving into JEE preparations, know the JEE syllabus and understand the basic concepts present in the syllabus.

Evaluate your knowledge on basic concepts.

Make notes on required topics.

Choose The Right Study Material

To know about the best books for JEE advance preparation you can follow the below mentioned link : https://engineering.careers360.com/articles/jee-advanced-preparation-tips

Solve JEE Advanced question papers

Solve previous years question paper has its own advantages, like

Helps you to understand the exam pattern.

Will help you in time management.

Helps to increase speed and accuracy.

Helps you to gain confidence.

Further, to know more about previous year jee advance question paper and syllabus pattern and much more, you can follow the below mentioned link : https://engineering.careers360.com/articles/jee-advanced-preparation-tips

Further, to follow the best books in JEE mains and advance you can follow below mentioned books :

JEE Main Books Important for Mathematics

Trigonometry by S. L. Loney

Higher Algebra by Hall & Knight

Maths XI & XII by NCERT

Coordinate Geometry by S. L. Loney

Problems in Calculus of One Variable by I.A. Maron

JEE Main Books for Physics

Problems in General Physics by I.E. Irodov

Fundamentals of Physics by Halliday, Resnick & Walker

Concepts of Physics Vol I and II by H.C. Verma

Books for JEE Main Chemistry

Organic Chemistry by Paula Bruice Yurkanis

Organic Chemistry by Morrison & Boyd

Inorganic Chemistry by J.D. Lee

Numerical Chemistry by P. Bahadur

Further, For more information and complete details about the JEE mains tips and strategies and about the subject wise weightage in JEE mains, you can follow the belwo link :

https://engineering.careers360.com/articles/jee-main-preparation-tips

I hope that this will help.