Yes, this should be possible. The document contains a processing-instruction with this information. You can retrieve this for example in the following way:

function getVersion(doc) {
  if (!doc) return false;
  var ish = doc.selectSingleNode("processing-instruction('ish')");
  if (!ish) return false;
  var result = ish.getTextContent().match("version=\"(.*?)\"");
  if (!result || result.length < 2) return false;
  return result[1];
}

getVersion(Editor.getActiveDocument());

Yes, this should be possible. The document contains a processing-instruction with this information. You can retrieve this for example in the following way:

function getVersion(doc) {
  if (!doc) return false;
  var ish = doc.selectSingleNode("processing-instruction('ish')");
  if (!ish) return false;
  var result = ish.getTextContent().match("version=\"(.*?)\"");
  if (!result || result.length < 2) return false;
  return result[1];
}

getVersion(Editor.getActiveDocument());

Yeah, the sample code you sent returns false and the raw xml returned by getXML() shows that the doctype deceleration is immediately followed by the concept tag. I would expect to see the ish PI between them. Im on Create 5.2.4 and Architect 11.0.2929.3.

Ok, that explains it, above snippet only works in 5.3/12.0.

Then still it should be possible, but using a different approach:

var activeDocument = SDL.Models.getItem(window.location.hash.substring(1));
SDL.Utils.Xml.getInnerText(activeDocument.getWrappedObject().getXmlDocument(), "/data/item/@version");

This still works in 2016, however it looks like the case of the attribute names on the data tag was switched from camel case to all lowercase.