Make the marinade: Soak the dried chiles in warm water until softened, about 15 minutes; drain. Discard the stems and seeds. Heat the vegetable oil in a medium saucepan over medium heat. Add the chiles, onion and garlic and cook, stirring, until the onion is translucent, about 5 minutes. Transfer to a blender and add the pineapple juice, orange juice, apple juice, beer, vinegar, oregano, paprika, annatto, cloves, 2 tablespoons salt and 1 tablespoon pepper; puree until smooth.
Make the tacos: Place the pork in a large roasting pan and pour the marinade on top; cover with foil and refrigerate at least 4 hours.
Preheat the oven to 350˚ F. Transfer the pork to the oven and roast, covered, 3 hours. Remove the pork from the braising liquid and transfer to a cutting board; let rest at least 10 minutes. Reserve the braising liquid. Cut the pork into 1/4-inch pieces and return to the braising liquid, tossing to coat.
Assemble the tacos: Arrange the pork on the tortillas and top with the pineapple-serrano salsa and tomatillo salsa. Top with cotija, chicharrónes, cilantro and radishes. Serve with lime wedges.
Soak 20 dried guajillo chiles in warm water at least 30 minutes; drain. Remove the stems and seeds. Transfer the chiles to a blender and add 4 cups water, 5 garlic cloves, 1 diced onion, 2 teaspoons each chicken stock and kosher salt, 1 teaspoon each pepper and dried oregano and 1/2 teaspoon cumin; puree. Strain through a fine-mesh sieve. Heat 2 tablespoons vegetable oil in a nonstick skillet over medium heat. Dip a tortilla in the chile mixture, then add to the skillet and cook until lightly browned, 1 minute per side. Remove and sprinkle with cotija cheese. Repeat to make about 30 tortillas.
Heat a grill to medium high. Peel 2 pineapples and cut into 1/4-inch-thick planks; grill until marked, about 3 minutes per side. Finely chop the pineapple, removing the core. Soak 2 to 3 thinly sliced serrano chiles in ice water, 10 minutes, then drain. Combine the pineapple, serranos, 2 diced small red onions, 1/2 cup chopped cilantro, 2 tablespoons lime juice, 2 teaspoons kosher salt and 1/2 teaspoon pepper in a bowl; toss. Refrigerate until ready to serve.