Questions about Apple Watch Series 3

Charging cable and black silicone wristband are included.

The invoice should be stored in your profile under Invoice. At least that's how it is for me.

Yep, that works.

The difference between the two watches is the supplier and the operating system. Because they are different suppliers and they set the prices, there can also be a difference between the same articles. The information is also correct :-)

In my experience, the battery is not a problem. I charge the watch overnight and so far the battery has not lost any noticeable power. Apple's charging management seems to be good, but there's one thing: if the battery is only charged to 95% at a time, it retains its full capacity much longer. The watch will probably have to be replaced before the battery gives out, because by then there will already be series 8 or 9, and series 3 will be hopelessly outdated. :-)