Yes, you need one minute for the plate and additional time for the food; check often to avoid overheating your food the extra time required depends on the amount and temperature of food, but you already know that don't you? .
No, the heating element is also made mainly of proprietary ceramic material; there are no dangerous liquids or PCMs (Phase Change Materials) inside the plate.that may leak..
Handle the hot plate by the rim and remember that the bottom also gets hot; the use of an individual table cloth ie recommended, do not use plastic.