Discourse backups are normally .tar.gz files that include the database, uploads, and metadata. An SQL dump plus .mnu/.des files don’t match the official Discourse backup format, so they can’t be restored through the standard admin restore workflow. If you still have access to the old trial instance, check for the proper .tar.gz backup.
For choosing a theme: the easiest way to get a feel for what’s available is to browse the curated themes on Meta. Most entries include screenshots, demos, and feature notes, which makes comparison a lot clearer than viewing them in Theme Creator alone.
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