Being an IAF Officer is dream of many, perhaps its not mandatory for one to pursue Aerospace or Aeronautical for joining Technical/Flying Branch of IAF. Even if you are from Mechanical or Electronics, you can always answer the AFCAT Exam and pursue a career in IAF.

Perhaps since you are interested in Aerospace, I would advise you to prepare for JEE Mains and Advanced. The Top 4 IITs have Aerospace Engineering in their Curriculum and perhaps they are one of the best in India. Besides IIT B, K, KGP and Madras, IIST Trivandrum is another good destination for Aerospace, Avionics and Electronics enthusiasts and has excellent Faculty, Infrastructure and Research Facilities. Other good technical institutes having Aerospace curriculum are Hindustan Institute of Technology Chennai, SRMIST Chennai, IIEST Shibpur and RV College of Engineering, Bengaluru.

All the best. For more information about Aerospace Engineering and Colleges in India do follow the link below

https://www.careers360.com/courses/aerospace-engineering-course