Try CapCut. It is free and simple.
- Install CapCut from the App Store.
- Open it, tap New project.
- Pick your video, tap Add.
- Select the clip on the timeline.
- Scroll tools at the bottom, tap Reverse.
- Wait for processing, then tap Export in the top right.
- Choose resolution, save to your Photos.
CapCut keeps audio in sync most of the time. If audio sounds weird, mute it in CapCut and add music or a new voiceover.