No it's not compulsory to have c++ in 12 th class.
But if you have knowledge of it it will helpful to understand in the college when there will be subject in engineering.
So it is not necessary but for sake of knowledge and experience you should do it.
But it doesn't effect your admission.
Good luck.

Hello
Priyanka
Yeah it will help you for more programming experience ...so that in ECE three or more programming languages will come in that one is C and C++ and other languages are open elective it will depends on interested languages
So if in 12th you have the C ++ it is advantage
Thanks