Pokemon-go – Will trading count towards thethical research Catch a Ditto

As it appears right now it is possible to get 146, all of which you can catch or evolve up. The 5 legendary (Articuno, Zapdos, Moltres, Mew, Mewtwo) are uncatchable at least at this time. Whether they are added later or will be rewards for something special is unknown.

Pokémon can have moves that don't match their type(s). You gain a STAB bonus for attacks that match your Pokémon's types, but otherwise it is just the attack's type (not your Pokémon's type) against the defender's type(s) in the type effectiveness chart.

In your specific case, the Dark type attack an your Poison/Flying Golbat does not receive any bonus damage from Golbat's typing, but a Dark typed move may help it against things like Psychic types which would likely have attacks that do extra damage to Poison types.