DD Support Board and Research Team

[Zorax]

Integral; Sorry to step on Sleepy, but ARC is incorporated in all versions of hdmi for some time for sending data to soundbars and accessories hopefully eliminating extra wiring in the process. As long as the newer TV also understands ARC. Which your Sony will and may have come with home theater goodies.
Output 3 may be what you need that plugged into if the cable feed is going to be your only source. But if you're going to use blueray, then you're going to want to leave the cable in #1 and the blue ray in #3, or whatever the ARC is labeled on. The TV typically does the routing after receiving the source to parts of the system. Not all, but most now do it.

https://hdguru.com/what-is-hdmi-arc-and-what-does-it-do-for-your-hdtv/