A:AnswerThe TX-NR646 supports a long list of formats. I've included a segment of the manual showing all of the HDMI capabilities. Most of the formats you list are supported.
A:AnswerThe two sub outputs are internally connected together and are setup for a one room configuration to support the other speakers in the main zone.
A:AnswerThis receiver is hdcp 2.2 compliant. I have attached a 4K player to the device and streamed 4k content and everything works perfectly - and beautifully.
A:AnswerThat is what I'm doing. Since there is no "formal" tape loop, I'm using Zone 2 pre out for that purpose. It is not as convenient, but it works.