Susan, you wrote:

1.      Is it required, or just a norm, to submit your article to one journal at a time and if rejected, move on to the next journal?  Or does it vary from publisher to publisher?

**It's required and I'm not aware of a field inside or outside of medicine that would consider OK to do anything else (LIS is the same!). This is one reason that publication can take a long time :(  See here:

http://icmje.org/recommendations/browse/publishing-and-editorial-issues/overlapping-publications.html 

2.      If a journal responds that you need to make specific changes/edits, does that mean you are in some sense accepted and you should not submit the article to another journal?  In that same situation, could you just decide you don't want to make the changes/edits and move on to another publisher in hopes less re-writing will be required?

**You aren't "in some sense accepted" unless the journal clearly responds that your paper has been accepted but requests revisions. Then you do those revisions. This is different from the situation in which a journal indicates they are interested but cannot make a *decision* without those revisions. 

It's always possible to pull a paper out from the review process as long as you clearly communicate that to the journal editors. A student of mine just had to do that after we had no decision after 2 years. (Yes, 2 years).