As per the latest eligibility criteria of CDS 2020, the candidates between 20 to 24 years are eligible to give this exam.
You are 23 now and you are going to be of 24 years on 5 March 2021, so you are eligible for the respective exam in each and every course ranging from IMA to OTA.
Refer here for more info - https://competition.careers360.com/articles/cds-exam#CDS-2020-I--II-Eligibility-Criteria
Feel free to ask doubts in the Comment Section.
I hope this information helps you.
To be eligible for Combined Defence Services Exam (CDS) candidates should be between 20 to 24 years of age and to be eligible for Air Force Common Admission Test 2020 (AFCAT) candidates for Flying branch must age between 20 and 24 years while those applying for Ground Duty (Technical and Non-Technical) branch must age between 20 to 26 years of age. As your age is 23 you will be eligible for CDS and AFCAT. Union Public Service Commission (UPSC) will release the CDS 2 2020 exam notification of August 5, 2020. UPSC CDS 2 Exam 2020 is scheduled to be held on November 8, 2020. So you can apply for CDS but the last date to fill online application form for AFCAT 2020 was July 14th 2020 so you cannot apply for AFCAT now.