Regarding SELCAL, The buttons you see are the lights that go on in addition to hearing the chime.
In simple terms, there aren't separate radios for SELCAL and comm. The SELCAL signal comes through your main comm radios - HF and VHF. You have to have the proper frequency tuned in (either HF or VHF) for ATC or company to chime you on SELCAL. No, the company can't tune your radio for you. For example all aircraft flying over water monitor AIRINC on HF for giving position reports and getting SELCAL messages. AIRINC isn't ATC, but rather a radio company that acts as a clearing-house for information between us and ATC. When ATC wants to give us a message, they call AIRINC, who then gives us a SELCAL on the HF frequency they previously told us to monitor. When they call us, a chime goes off, and the light on the appropriate overhead button illuminates, telling us which radio they're calling us on. We push the button to extinguish the light (or on some planes, keying the microphone also extinguishes the light) and talk to whoever is calling us. Over land, if ACARS is inop, we keep one of the VHF radios tuned to the appropriate AIRINC frequency for wherever we are, and the SELCAL signal comes over that radio. But if ACARS is operational, we don't have to keep one of the VHF radios listening to AIRINC. Our 767's all have three VHF radios - one dedicated to ACARS, and two for talking to ATC. If the ACARS is inop, that radio would be tuned to the AIRINC frequency (as described above) to listen for the SELCAL chime.
In the photograph in the first post, it appears the plane has only two VHF radios, along with the two HF radios - hence only two buttons on the SELCAL panel.
In our newest planes, those button-lights for SELCAL have been removed. When we get a SELCAL, a message appears on the EICAS screen, and the appropriate switch on our audio panel lights up with a "call" light above the volume dial for that radio. The only button-lights left on the overhead panel are the cabin call buttons from the F/A's panels.
Hope this helps.
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.