All galaxies are old and formed towards the beginning of the universe. Some of the more isolated ones, if they haven't interacted gravitationally, remain small and are not overly active.
Not all galaxies have SMBHs at their centre. Spiral and elliptical galaxies do but I doubt most irregular dwarf galaxies would. They would undoubtedly contain stellar mass black holes along to possibly having those elusive intermediate mass (100-10,000 solar mass) ones. Supermassive black holes largely form through galaxy interactions, whether it be through gravitational interactions driving black holes into the centre OR massive black hole mergers between dwarf and larger galaxies.
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