No. In fact, a function can't have an answer at all, because it's not a question. An equation has an answer, and possibly more than one. In general, an equation is in the form of (one function) =...
yes, look at the function f(x)=3x^2
The antiderivative is x^3+C where C is the constant and is more than one value for C.
In fact, 3x^2 will have an infinite number of antiderivatives.