#1 Yes. For personal use (like a 1-on-1 language exchange), the free version comes with:
- 1-on-1 Calls: These are generally unlimited in duration (up to 30 hours) - feel free to turn off the camera*
- Group Calls: If you eventually add more people, the free limit is 60 minutes.
- Chat & Files: You get unlimited chat history and 5 GB of cloud storage for sharing language worksheets or notes.
#2 You only need one app which is (Microsoft Teams) it's available on PC/Laptop/MacOS/Mobile
Adding it's including useful features for your case (Inline Translation + Live Captions)