Yes, but it depends on your provider. There’s an overview of providers that work well and providers that don’t for the Xperia 10 II and III over here, and a similar overview for the C2 over here. Keep in mind that these are just users who decided to share their results, and many results are nearly four years old from a test way back when VoLTE support in Sailfish was first introduced. Probably many more providers work well now.
It isn’t, but it’s coming.
Yes and no, the community came up with a useful hack, but Jolla took a different approach to make it work the way people would expect it to. But maybe the community hack pushed Jolla to prioritise their work on Bluetooth support for Android applications.