Hi,

The CDS Exam is conducted for recruitment to the Indian Military Academy (IMA), Indian Naval Academy (INA), Air Force Academy (AFA), and Officer Training Academy (OTA). Candidates can apply for CDS, but make sure you are completing your degree before the date of joining.

You are currently in your third year of graduation in chemical engineering. Any student of any engineering branch can appear for CDS exam. ... You can appear for CDS when you are in your final year if the degree, that means if you are in a program of 4 years then you can give paper from 7th semester.

Hope this helps

Wish you luck