New Phone - New questions

Hi,

I have the HTC M8 European model and I have a few questions:

1. VoLTE (4G Voice and Wi-Fi calling) can be enabled in the stock HTC software or CM 13 ?
2.Turning off DT2W will save battery ?
3.Any AOSP 7.0 availabale for tests ?
4. Any tricks that should know about the device ?

Thanks !

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