1. To allow users to preview content before purchasing, do you just link to content in .mm file using WAP <go> tag?
2. Is it possible to proactively Push the previewable content to the user any other way?
RE: What is the WAP tag for previewable content?
No, the previewable content is packaged in the .mm file with preview rights and delivered to the user as explained in the documentation. If (s)he then decides to buy the content (s)he receives an other package with the save rights. So both the rights and content are included in the .mm file, not only links to the content.
2. Delivering Preview-enabled content by other means than WAP download is not supported in 3410.