Beef tongue is too large and unwieldly to deal with. Stick with veal tongue. The meat stays more supple after you boil it for 2 hours.
Pork kidneys are a decent, cheap substitute for lamb kidneys. But lamb kidneys, although smaller, are much tastier. Chicken gizzards and livers are cheapest. Chicken hearts are expensive and not worth it, although they are soft.
The white connective tissue in chicken gizzards can be softened by boiling them in a pot for an hour. After that, proceed with your recipe.
Chicken livers can be baked in an oven at 350 degrees F for 35 minutes, in a glassware baking pan. Leaving chicken livers on aluminum foil is a no-no, they will melt into the aluminum foil. Use glassware, coated with olive oil.
Recipes for something like banana loaf (which is neither a bread nor a cake, but something in between), if they ask for two cups of flour, will make more cake than a single individual can handle in two weeks. Typically, for a single individual, recipes that ask for one cup of flour are sufficient. Look at a typical Betty Crocker cake mix box. That’s all the flour (and sugar) one person would need to make a dessert that would last 10 days.
Lemon zest is an over-rated ingredient. If you must have lemon juice in a dessert recipe, bottled lemon juice works just as well. They even have bottles of “lemon extract” and “orange extract” in the section of the supermarket where they have vanilla extract.
In fruitcake, the fruit pieces MUST be dried, like prune or raisins. Wet fruit will stay wet after the cake is baked. This will lead to spoilage. Also, golden raisins are expensive and over-rated. As are currants (a type of grape that is treated to end up like a raisin).
Never cook your meat at too high a temperature for too long a time. THESE are the cardinal sins of cooking.
Regardless of what a recipe says, or what you’ve seen on YouTube, you have to experiment. Failure is the best teacher.