Hello,

The upper age limit to appear for JEE Advanced is 25 years. A candidate can appear for JEE Advanced for two consecutive years from the year of passing in the qualifying examination. Suppose that if you have passed 10+2 in the year 2021, you can appear for JEE Advanced 2021 and JEE Advanced 2022. If you repeat class 11th and  class 12th you can again appear for JEE Advanced for two consecutive years provided you must qualify in JEE Main in the respective year. As there is not bar on gap in education between class 10th and class 12th you can appear for JEE Main and JEE Advanced provided you must fulfill the eligibility criteria.

To check more details you can use the link below

https://engineering.careers360.com/articles/jee-advanced-eligibility-criteria