The western key part is in the beach area, near one of the fields. The is a small easy to miss path.
Both tf episodes are tied to the broken key quest.
Was researching part two the search for ancient stone tablets? If so you know which ancient stone tablets did you find?
Was the mermaid quest to find the rare sea shell? If so it is underwater. If i remember correctly the south-western plains.
I dont know from the name allone what quest of collection and demon hunt were. Would need to see the quest description to tell.
Also hope this is at least some good starting help with the quest. Feel free to ask more!