Hi, I think it's compatible. I myself have a Huawei p10 and the watch connects to the phone via bluetooth without any problem. It's a good idea to have a watch that is compatible with all the other phones in the world.

No, not directly during the activity. However, this is calculated afterwards when uploading to Garmin Connect (or Strava, for example) and displayed accordingly. Best regards Chris

The box contains an instruction leaflet which is enough to set up the watch with defaults. However the full manual is available online (https://goo.gl/86M7SN) which describes all the views (there are many) and features.

Hello David I bought the 235 about 4 months ago to replace my 220, partly because of the integrated heart rate measurement (on the wrist). I was a bit unsure at the beginning and was actually convinced that I would wear the chest strap during running training anyway. However, it quickly turned out that the heart rate measurement on the wrist is really very accurate. It may react a little more slowly to rapid changes in heart rate (e.g. during intervals) than the measurement with the chest strap, but this is negligible. So now I don't wear a chest strap during running training, only during training or races with the cross-bike. However, a prerequisite for accurate measurement is that you don't put the wristband on too loosely. I hope I was able to help you with this. Best regards Chris

Yes, a USB charging cable is included in the scope of delivery, this is also used immediately for data transfer via "Garmin Connect" on the PC. You can also synchronise your data with the mobile app "Garmin Connect Mobile" via Bluetooth. Enclosed is an unboxing video: https://www.youtube.com/watch?v=vmCUBFJWIdI or a bit more detailed if you like to read: http://fitnessmodern.de/garmin-forerunner-235-test-smarte-gps-laufuhr-mit-pulssensor/