May I know if there are ways to download web-based InfoPath form from a SharePoint Site and view it under a InfoPath Viewer?
You can easily open it in InfoPath client application by selecting
Edit it Microsoft InfoPath from ECB (list item) menu.
Since InfoPath web-based form is XML document you can also use
SendTo > Download a Copy from same menu to locally save your form as XML. You can then open saved XML in InfoPath.
However, keep in mind that you need access to xsn template to properly view and edit your form (access to SP where xsn template is published)