a direct criminal appeal is completely useless without the trial attorney making doubly sure that any appellate issues were properly preserved for the appeal or beyond. In this sense, what you don’t know can hurt you, badly. And you must have lost and been convicted (otherwise, an appeal has no purpose).
There are no “do-overs” usually in criminal court when a defendant “freely,” “voluntarily,” and “intelligently” enters a guilty plea with the “assistance” of “competent counsel.” Once the plea is entered, accepted by the court, and the defendant is sentenced- – the defendant must live with the whole ordeal (even if the defendant is unsatisfied for whatever reason). There is no redo or rework or second chance, and the plea is final in most respects.