I have iOS. Notifications that you receive on the lock screen of the iPhone also appear on the watch. But you can't read the full message. I can't say whether it works with the LTE version, when all the communication also takes place directly on the watch.
Incoming calls are also displayed and can be answered. However, the call has to be made on the phone. This already helps me, because during a meeting, for example, I don't have to keep looking at my phone but can see immediately on the watch who is writing or calling.

No

I can't answer that,, don't have ios.