Proprietary cables are hardly new, and to be fair those cables and connectors are usually way better than the standard stuff. Firewire and thunderbolt were actually released as open standards and saw decent adoption. Lightning is far superior to Micro-USB. Just listen to the wailing and gnashing of teeth by Macbook owners having to give up proprietary MagSafe for USB-C charging on their laptops.
XCode is free and has been for ages. To this day you can develop whatever you like for the Mac and not pay Apple a penny. You don’t even have to use XCode to do it. It’s even free for iPhone development for your own device now, though you have to pay a fee to publish stuff. I’m not sure what you comment about emulators is about to be honest, The iOS emulator for the Mac is free.
Yes they want their cut from Spotify. I don’t understand the Apple exceptionalism about this though. Nobody rages on HN about Sony’s monopoly over games development for the PlayStation, or Microsoft for XBOX, or Nintendo for the Switch, but for some reason Apple which came to this business model two generations late is the root of all evil. It really is kind of weird how that works. Maybe if their iconic image was a cute little plumber instead of a half eaten fruit, everyone would say 'Aww how cute' and give them a pass.