If you are talking about this product: Garmin Instinct (45 mm, Polymer) only difference is the supplier.
The brand does not mention this detail unfortunately. In my opinion, you will have to use Bluetooth with your phone to synchronise the data.
ok, because you write: "only change the strap". You can put any 22 mm strap you want on it. it has a snap closure for changing, so it's very easy. but the silicone is great for sports.
This watch doesn't need a chest strap, the heart rate monitor is pretty accurate. If you want a watch with a chest strap, get one that comes with one. i don't think it needs one. it's very accurate.