CDS

According to your documents, at 23 years and 5 months old, you meet the age criteria for both the Indian Military Academy (IMA) and Officers' Training Academy (OTA) through the CDS2 examination.the official age limits are 

IMA: Unmarried male candidates born between July 2,2001, and July 1,2006.

OTA: Unmarried male candidates born between July 2,2000, and July 1,2006.

Since eligibity is based on date of birth mentioned on the documents, age 22 years doesn't affect your application.

CDS 1 2025 application form correction window was closed. The authority extended the last date to apply for the CDS 1 2025. The last date to apply for CDS 1 2025 was January 1, 2025.

Combined Defence Services (CDS) exam but not for the National Defence Academy (NDA) exam. 
Eligibility:
NDA: It is also available for those who have successfully completed their Class 12 education. However, in this case, you would not be eligible because the age limit for NDA ranges between 16.5 to 19.5 years and you are above that.
CDS: Candidates must have graduated or be in the final year of their graduation. CDS age limit is 19 to 25 years. So, you are eligible for this exam considering your age and educational qualification.

Your sister can surely give the CDS exam. Since she is class 12 and studying Biology, she needs to complete her graduation first, as CDS exam requires candidates to be a graduate from any recognised university.

Any OBC girl is free to apply for the CDS-I examination under reservation benefits extended by the government.

The eligibility of OBCs, including girls, is similar to that of general categories regarding age and educational qualifications. However, here his age limit has been relaxed and certain seats earmarked for OBC candidates.

check the latest notification from the CDS exam regarding any change in criteria. In this way, OBC girls would be eligible to take this exam as long as they fit the educational and age qualifications and the corresponding reservation can be claimed.

Now CDS exam  application is processed through OTR that is one time registration you can edit your form when the correction window is opened by UPSC make sure to correct it before the deadline. This correction window is opened around 10 to 12 days after the last date of submission of application.

Yes, you can apply for the CDS exam 2024 but it depends on the academy that you want to opt for. As for the IMS BMAS, INA & AFA, the applicant is age 19-24 years for having been born between 02-01-2001 & 01-01-2006. Nevertheless, for the OTA, the age must be in the range of 19-25 years and you should have been born after January 2, 2000, and before January 1, 2006. As you are born on 21st March 1999 you are complex for the OTA application. The application fee for appearing in the CDS exam is Rs 200 but the SC, ST candidates along with the females are eligible for fee exemption.