Can CYK Parsing algorithm generate the parsing tree in O(n^3)?
It depends what you mean by build a parse tree.

You can build a parse forest in $O(n^3)$ time and space. The forest represents all parse trees, even an infinite number of parse trees, because it is a graph, not a tree. From a parse forest, it is possible to produce a single parse tree in time linear to the size of the forest, and it is possible to iterate through all possible parses.

So if you either consider that "build a parse tree" means "find one of the possible parses" or if you consider that it means "build a datastructure which represents all possible parses", then you can certainly do that with a CYK grammar in $O(n^3)$.

If, on the other hand, you intend "build a parse tree" to mean "build all parse trees for a sentence", then it is not limited to exponential time; it is easy to write a grammar with an infinite number of possible parses for certain sentences.