If the states request a general revision of the Constitution, then it can address amendment proposals on any subject it wished. But not until. That potential aganda I listed is what might happen if the states requested an open convention to address any subject.
Failing such all-encompassing language, a convention would be restricted to the subject(s) that the states requested it to address.
Yes, but how do you keep the convention from simply ignoring the restrictions? Politicians don't like restrictions on their authority.
As I said, the Constitutional Convention was a "ruanway" convention that exceeded its mandate to amend the Articles of Confederation.