Whisk together the chile powder, salt, paprika, onion powder, garlic powder, pepper and 2 tablespoons of the sugar in a small bowl until completely combined and no lumps remain. Spread the mixture evenly over the ribs, pressing it into the flesh on all sides. Let sit at room temperature for at least 1 hour or wrap tightly with plastic wrap and let sit, refrigerated, for up to 48 hours.
When ready to cook the ribs, add the apple cider to a 6-quart Instant Pot®. Set the rack in the bottom of the pot and stand the ribs up on the rack so the bones are pointing up and down, coiling both rib racks around the perimeter of the pot.
Follow the manufacturer's guide for locking the lid and preparing to cook. Set to pressure cook on high for 35 minutes.
After the pressure-cook cycle is complete, follow the manufacturer's guide for natural release. After 15 minutes, being careful of any remaining steam, unlock and remove the lid.
Let the ribs sit, uncovered, to cool slightly, about 10 minutes (if you try and move the ribs while they are hot, they will fall apart). Transfer the ribs to a rack set inside a baking sheet and let sit until cool enough to handle, about 10 minutes more.
When cool enough to handle, remove the bones; they will be loose enough to pull out of the rack with little or no resistance. Using small tongs, pliers or your fingers, pinch each bone on the larger, exposed end and jostle to loosen, then pull straight back to remove. You may have to hold the meat in place when you pull the bones. Discard the bones. Tent the ribs with foil and set aside until ready to sauce.
Meanwhile, remove the rack and set the pot to high saute. Add the barbecue sauce, ketchup, mustard, Worcestershire and remaining 1/2 cup sugar and cook, stirring frequently, until the sauce is reduced and thickened, 20 to 25 minutes.
Position an oven rack in the highest position in the oven and set to broil on high.
Generously brush the ribs with the sauce and broil until the sauce is bubbling and browning in spots, 1 to 4 minutes, depending on your broiler. Reserve the remaining sauce for serving.
Combine the butter and garlic in a small bowl and brush liberally over the entire surface of both loaves of bread, crust and cut sides. Toast the bread on a baking sheet under the broiler, 1 to 2 minutes per side.
Place one rack of ribs on the bottom half of each loaf meaty-side up. Drizzle with the remaining sauce and top with the pickles, onions and the top half of the loaf. Cut into 3-inch sandwiches and serve with chips.
Settings may vary on your Instant Pot® depending on the model. Please refer to the manufacturer's guide.
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