Naval Officer

After or while 12th, you can apply for NDA Entrance Exam. And after 12th, you can TES 10+2 Navy Wich requires minimum 70% in PCM and should have appeared 12th.In NDA , you have to pass the Written exam and after then you have to go for 5 days SSB interview. And if selected then medical and merit. In TES students are selected on the basis of 12th and JEE score. And after that, they are called for SSB interview and then medical and merit. For more information, go to Joinindiannavy.

Yes, you can join, but for that you have to apply and clear NDA procedure and after that you will be given choice of opting for, after that you can be able to join Indian Navy or you can also opt for the TES.

Hi,
With 54% marks, you won't get any good college. First of all you apply for a reappear and if your aim is only getting B.Tech degree you can take admission in Chandigarh University. Last year they were selling seats of B.Tech for Rs.10000. Even the IT companies demand for at least 60% marks in class 12th. All the best for your future.

Yes, girls can opt for navy and army as a career. Admission process varies for every post:
For Indian Army
1. UPSC Entry
2. NCC Special entry
3. SSC-Technical Entry
4. JAG entry
For Indian Navy
1. SSC GS (X)
2. SSC Engineering
3. SSC - Pilot/Observor
4. Education Branch
5. SSC Logistics
https://www.shiksha.com/careers/army-officer-14
https://www.shiksha.com/careers/naval-officer-82

Yes, you can join merchant navy after B.Sc in computer science. For more details, check out the link below:
https://www.shiksha.com/careers/merchant-navy-officer-77

It is a bit tough, because there is no direct relation with B.Sc computer science and maritime skills. If the age and fitness factors are in compliance, you may be lucky. To check the detailed criteria, please see here-
http://dgshipping.gov.in/WriteReadData/CMS/Documents/201606131056371994392Eligibility_criteria_trg.pdf

Read this article it will help to make a wide perception about this field. https://www.shiksha.com/careers/merchant-navy-officer-77
You can get valuable information regarding merchant navy here. https://www.marineinsight.com/careers-2/merchant-navy-recruitment-process-entrance-exam-salary-and-jobs/amp/.

Check the below mentioned link for all the information:
https://ask.shiksha.com/careers/merchant-navy-officer-77

Yes, you can apply for Navy after the completion of your 10th class also.

Yes, he can do fellow programme in management in IIMs. These courses are meant for highly experienced aspirants. In your case by serving nation your friend might have learned various management techniques in day to day operations. Go through IIM A, B, C and other IIM websites go through their course called Fellow Programme in Management.
All the best!