1.) You can check this inside your style.css (wp-content\themes\broadscope\style.css). Inside that file you can see something that looks like this:
Theme Name: Broadscope
Description: <strong>A sleek Business Theme by Kriesi</strong> - <br/> Update notifications available on twitter and facebook:<br/> <a href='http://twitter.com/kriesi'>Follow me on twitter</a><br/> - <a href='http://www.facebook.com/pages/Kriesi/333648177216'>Join the Facebook Group</a>
Author URI: http://www.kriesi.at
2.) You can check this link: http://www.kriesi.at/support/topic/latest-theme-updates-please-check-if-yourre-using-an-outdated-theme-version
3.) You can download it in: http://themeforest.net/
4.) We don't have any notifications if there are updates or new version of the theme. However, we regularly update this link: http://www.kriesi.at/support/topic/latest-theme-updates-please-check-if-yourre-using-an-outdated-theme-version on a regular basis so you can check if you have the latest version of your theme.
5.) Unzip the file that you can download from themeforest(broadscope.zip). Inside it you can see these folders _MACOSX, documentation, psd, etc. and a file named "version_broadscope.rtf". This file contains the changelogs.
6.) You can do this via ftp, just replace the old parent theme (broadscope) with the latest version of the broadscope theme.
Hope this is helpful. :)