This is used mostly in fried squid recipe. Cook squid briefly before cutting or braise it long enough for it to toughen and then become tender again. A popular method for quick cooking is to cut the bodies into rounds, coat in breading and deep-fry. Stir-frying and sautéing works well by putting a lot of oil.
Do squid needs flour and cornstarch for it to be crispy?
Yes, that is for the batter. If you have an oven and want that super crispy squid, reheat the calamari from frozen, set the oven to 400°F (200°C), spread the calamari out on a wire rack or baking tray, and heat them for 10 minutes. Still, do not forget to soak them in vinegar for 30 minutes.