After 16 hours of searching, I could not find comprehensive answers to the following questions:
What's the modern PC, Android and Apple pinout standard inside the 3.5mm TRRS female socket? Is it CTIA? Is it the same for all modern headphones/headsets/earphones with TRRS male plugs?
Or do some PC, Android and Apple device sockets and earphone plugs have a different pinout configuration?
Are there known incompatible plug/socket or M/F TRRS brands or products?
Are the Iphone headsets/earphones fully compatible with PC and Android? And vice versa?
What exactly happens when a headset TRRS plug is fully inserted into a socket? Does it automatically disconnect/disable the PC's speakers and microphone and connect/enable those of the headset?
Do external headsets/earphones with TRRS male plugs require new drivers to work properly with PCs? [never, sometimes, in most cases, often, always]