Explanation:

- Hima Das: She is a prominent Indian sprinter and has earned accolades for her performances on the track, including a gold medal at the Asian Games. Hima Das was indeed appointed as the first ever youth ambassador of UNICEF India.

- Jisna Mathew: Indian athlete specializing in sprint events, but not known to have held the position with UNICEF.

- Mandeep Kaur: Another Indian sprinter, but not the person appointed as UNICEF India's youth ambassador.

- Manjeet Kaur: A former Indian track and field athlete, known for her contributions in relay races, but not the one associated with the UNICEF role.