Because I said so : 내가 그렇게 말했기 때문에

신경 is concern. While, 걱정 is worries. 신경 써요 = to put concern/care/notice about something 걱정해요 = to put worries about something

Dindin's answer is right. Takutnya does not mean you are afraid of something. It means that you are worried about something. In korean, it is really the same with 을/ㄹ까봐 비가 올까봐 우산 가져왔어요 Worried that it might rain, I brought an umbrella. Takutnya nanti akan hujan, aku membawa payung.

As a native speaker, I too become confused with the sentence, provided with unclear context. But looking at the equivalent sentence in English, it all the pretty make sense. I want to add : The fact that the speaker are owning them becomes useful to the volcanoes and the flower (maybe he/she took good care of them ?)

Both have almost the same meaning. But remember, you wouldn't use ㄹ/을까(요) to ask someone what they want to do if you are not doing with them. Ex : 커피를 마실래요? Would you want to have coffee ? (Asking if the listener want some coffee, doesnt necessarily mean the speaker want it to) Or Shall we have coffee ? (If you are in group and refering to group context) 커피를 마실까요? Shall we have coffee ? (The speaker is asking if the listener want to have some coffee together with the speaker)

Then does 걸어드려요 means "to put down a tag?"