If you have access to another Mac running iMovie 10.2.5, you can manually transfer the application. On the source Mac, open the folder.
If prompted, click to accept an older, compatible version. Method 2: Extracting from an Older Mac imovie 10.2.5 dmg
Most users can simply download iMovie from the Mac App Store. However, users look for a specific "iMovie 10.2.5 DMG" file for several distinct reasons: If you have access to another Mac running iMovie 10
A prompt will appear asking if you are sure. Click again. "Incompatible Archive" open the folder. If prompted
Right-click (or Control-click) the iMovie app icon in your Applications folder. Click .