to 1.) passive filters contain no amplifiers; for pole Q´s larger than 0.5 (good selectivity), coils (inductances) are required. As coils have bad properties (heavy, expensive, radiating, EMC-sensitive,..) their function can be replaced by specific amplifier arrangements. That are actice filters.
In many cases, passive filters contain also coils (inductances).
Active filters can be implemented with opamps or OTA´s or Current Conveyors or suitable combinations; active filters have NOT always gain associated with them.
In some cases active elements are used simply to simulate the behaviour of inductances in standard passive ladder structures.