Will learning C help in learning objective C?

Answer 1

yes

Answer 2

If you know the concept of object oriented programming , and some basic stuffs of c++ , then you will proceed for learning objective C

Answer 3

Yes, objective​ c is supposed to be a better super set of c then c++. There is only a few extra things to learn to add object oriented concepts. For iOS development you​ also have to learn the Apple frameworks. Apple would recommend you just learn Swift instead of objective​ c.
Note I I'm not an expert on objective c, or iOS development.