Is it possible to insert a reference/hyperlink in one FrameMaker document to a section in another FrameMaker document (e.g. Refer to section 2. in document "B") whereby if the section changes in the second in the second document, the reference/hyperlink will be updated in the first document?
Your links should continue to work, as long as the relative positions between the source and destination documents remains constant, and there are no "missing resource" dialogs preventing the source document from opening.
However, the links between documents won't survive the PDF or online publishing unless they're linked into the same output. In other words, PDF links will not (without extra work) open up a PDF of your other document.