What is the appellant's burden to prove that the demurrer was sustained erroneously?

"The fact that we examine the complaint de novo does not mean that plaintiffs need only tender the complaint and hope we can discern a cause of action. It is plaintiffs' burden to show . . . that the demurrer was sustained erroneously . . . ." (Keyes v. Bowen (2010) 189 Cal.App.4th 647, 655.) It is a fundamental rule of appellate practice that "the trial court's judgment is presumed to be correct, and the appellant has the burden to prove otherwise by presenting legal authority on each point made and factual analysis, supported by appropriate citations to the material facts in the record; otherwise, the argument may be deemed forfeited." (Ibid.) "It is the appellant's responsibility to support claims of error with citation and authority; this court is not obligated to perform that function on the appellant's behalf." (Id. at p. 656.) "[T]he appellant must present each point separately in the opening brief under an appropriate heading, showing the nature of the question to be presented and the point to be made; otherwise, the point will be forfeited." (Ibid.)