0
Yes it is obtainable in plant population
Unobtainable.
There is no word yet as to how Darkrai will be obtainable. Most likely it will be through some sort of real world event.
Ore-wise, it's Coal. But stone, is (obviously) the most obtainable material.
you can't because he is an un-obtainable boss character,and he is one of the kowloon co. the only digimon that are not obtainable.