No, not all clear coats are lacquer, there are , enamel, lacquer, acrylic ,urethane clear coats, just like the paints, its always best to use the same type of paint and clear, meaning, if you use enamel paints, use enamel clear, there are always exceptions, like you can use urethane clear over pretty much all paints. Yes, its primer, paint, clear, in that order, and no, you only want to clear coat body parts that have been painted body color , as for the interior's, no you don't want to gloss clear coat the interior, the only time interiors would have a sheen would be if you were trying to replicate leather. Now, at the same time, interiors are not completely flat either, matte or satin paints would work for interiors.