Microsoft purchased Clipchamp and integrated it into Windows. It is a web-based desktop app.

Yes. Both BlueStacks and LDPlayer support Windows 8.1.

: Use the emulator’s "Shared Folder" feature to move video files from your Windows folders into the app for editing. System Requirements for Emulators

: Unlike many free mobile editors, it does not show banner ads while you are working.

In BlueStacks, use the "Media Manager" (usually a folder icon on the side toolbar). Click "Import from Windows" and select your MP4 or MOV files. Avoid HEVC codec files – convert them to H.264 first using HandBrake.