There's also that the copyright page on the physical editions should, if the publishers understand how these things are supposed to work, have some indication that it's a revised edition or later printing; in this case, technically, there should be a new ISBN, but I wouldn't hold my breath about that.
Yes, revised editions are marked as such on the bottom of copyright pages.
Unfortunately, they still share the same ISBN, which turns getting the right version of the book into a lottery while ordering online, which is an only option for a decent amount of people.
They aren't supposed to; reuse the ISBN with a revised edition. That's a no-no.
Yes, it's done all the time, but they are supposed to obtain a new ISBN if there are substantive changes to the work. Substantive changes can be pretty durn minor in reality.
There are regulations concerning the use of ISBNs and ISSNs, but there isn't an enforcement arm so publishers get away with this shit
Librarians hate it when they do this.
I worked in ILL at the Chicago Public Library's central library for four years... this is one of those things you continue reacting to some 29 years later... grimace