If you are looking for iMovie 10.2.5 specifically, you likely need a legacy version for an older version of macOS (such as macOS High Sierra, Mojave, or Catalina) or prefer a standalone DMG installer over the Mac App Store.
Most Mac users today are pushed toward the Mac App Store, which always serves the latest version (currently 10.4.x). However, the demand for a 10.2.5 DMG usually stems from: Imovie 10.2.5 Download Dmg
Confirm Legacy Version: If your current macOS is older (like Catalina), a prompt will appear asking if you want to "Download the last compatible version". Click Download to install version 10.2.5. System Requirements How to Download & Install iMovie 10
If you are encountering installation errors, Apple Community experts often suggest moving your current (non-working) iMovie app to the Trash (without emptying it) before attempting a redownload from the App Store to "reset" the store's detection of your installed version. ICS 1-to-1 - iMovie - Google Imovie 10.2.5 Download Dmg
MacUpdate: Provides technical specs and verified download links for various iMovie versions MacUpdate.