You can get the version of the host by using "xfa.host.version" command.
You can freeze (mean you can make the form non editable) but may be you can not stop the user to Print the form.
You can make the form readonly by making the access property of the top most subform to "readOnly".
Other approach you can consider is if the version does not match then display a messagebox to the user to download a newer version and close the app by using "app.execMenuItem("Close");" command.
Thanks
Srini