In her debut movie, nirosha had used a different name. what was the name? which was the movie and why did they decide to change the name?

The movie was soorasamharam ( yes. thats her first movie not agninakshatram)

She was rechristened as Mythili.

Reason: the director thought people will confuse her name with a condom :)

However, her name was retained in Agninakshatram, where she was more visible and the name nirosha stuck