I don't know the answers to most of these questions, and any answers I might give would be very uninteresting. I write because it's just something I have always enjoyed doing. My mom encouraged me to read and write since I was very young. I had a short story in a book fair in Norfolk, VA when I was in the 2nd grade, and my mom was very excited about it. I guess that's what got me going as far as interest in writing is concerned.
I don't remember why, but I got very interested in reading poetry when I was 13 or 14 years old. I bought books and checked books out of libraries, mostly written by the classic poets such as Milton, Blake, Coleridge, Browning, etc etc. All way over my head, but I thought if I read them all I would at least learn something. I had a copy of Master Poems of the English Language published 1966 and edited by Oscar Williams that I really liked and read all the time. I think it started with a poem by Chaucer and ended with one by Dylan Thomas.
Ideas for poems usually come to me out of the blue. I'll have a thought that sounds like a line in a poem or maybe the title of one. I'll dwell on it for a while, and if something more comes to me I try to get it written before I forget about it. Once I have the poem down beginning to end I look it over and edit it, usually several times, until I say to myself: "well, I guess that's it." Very common for me to edit poems over a period of years as I look at them, now and then. I read someplace "the best way to kill a poem is to have it published." I can't find the quote online.
Advice I would give a young writer is for him/her to not be instantly in love with first drafts. Just assume editing will be required, and look forward to doing it. Forget all that "writing from the heart" crap. There is no such thing. The heart is merely a pump. Pumps don't come up with ideas or creativity. Don't write poems just because you want to be a poet. Write only when you are inspired by an idea that is truly original (as possible) and interesting. As Charles Bukowski said: "Don't try." If you have to try, your endeavor isn't genuine.
Advice I would give full stop? Don't play the ponies. I like La Femme Royale in the 1st at Churchill Downs.