Explanation:

All of the above statements are correct.

• Agnipath Scheme allows patriotic and motivated youth to serve in the Armed Forces for a period of four years.
• Under this scheme, the youth joining the army will be called Agniveer. Youth will be able to be recruited into the army for a short duration.
• Under the new scheme, around 45,000 to 50,000 soldiers will be recruited annually, and most will leave the service in just four years.
• However, after four years, only 25 % of the batch will be recruited back into their respective services, for a period of 15 years.
• Aspirants between the ages of 17.5 years and 21 years will be eligible to apply. 
• Once selected, the aspirants will go through training for six months and then will be deployed for three and a half years.
• At the end of the four-year period, each soldier will get Rs 11.71 lakh as a lump sum amount, which will be tax-free.

Hence option 4th is correct.