I needed a way to get a Version via a HTTP-call and start a preview-edit-mode of a Web-Page. Think of editing SmartSections in Preview mode.
This is my way:
Make a call to manage_addPreviewVersion (see PreviewVersion_example in demo-directory) And than start working with SmartSections After all call manage_save or manage_discard of the PreviewVersion.
If your Browsers crashes while working in a version the cookie will life 30 days until leaving a version.