Explain the meaning of the sentence "Once you've learnt to use it, there's no end to what you can do"

"Once you've learned to use it" must indicate that you've mastered something, and once you've mastered this thing you could maybe evolve it and keep evolving it as said in this qoute "there's no end to what you can do" since you've already mastered it.

I'm not sure about this answer but I tried my best to help.

yes they most likly are and have planed t try to bring human life and supplies there also(due to global warming and other harmful resorces)

"a" because he is appealing to logic as oppose to appealing to the audience's emotions.