"Questions about copyright vis a vis Blockchain publication"

As a young man, I wrote a song, I paid to have it copyrighted.
During that time, and even now in times since then, I've been told that "you can place a copy of something in an envelope and MAIL it to yourself or someone you trust, and as long as the envelope seal was unbroken, that post mark date on the envelope serves as your proof that you indeed, were the author/composer of the work enclosed."
Should you find your work copied and claimed by someone else, or Plagiarized, you would have your letter as proof that you wrote it first.
So now, I'm wondering.

I am told that everything you and I write and post here in Steemit, is forever encrypted and encoded in the Blockchain.
So, by placing my name, the © symbol and the date on my writings, is the Blockchain record of my writing, tantamount to a copyright?

If I found someone had copied my works and published them elsewhere, could I use this electronic record as a means of proving my ownership of the material?
This is my way of asking an open question of those who know more than I do about this new [to me] medium of expression.
I would appreciate any serious input and commentary.
Thank you in advance.