I am finished making my first game. Now I want to publish it for IOS and Android. If I publish to IOS, it seems that I need to buy a mac. Would I run into trouble if I bought an older mac? Should I just get a brand new one? Does it matter what version of xcode I use?
1. As long as you can install Catalina (10.15) you are fine. In short any Mac made after 2013 are fine, but some older models are still supported. The full list of Mac computers with Catalina supports are shown here: https://support.apple.com/en-us/HT210222 As of now Xcode 11.3 still supports Mojave (10.14). So your choices are even larger. But it's better to buy a fairly recent one (2015 and upper), new or used, to extend your mileage, since Apple has a habit of limiting Xcode support to new macOS versions. 2. Yes, Xcode versions DO matter. Apple would always require developers to build their apps with newest Xcode available when they upload the binary to App Store Connect. They do have a grace period of a few months for older major version of Xcode, but it is only that long. Right now, you have to use Xcode 11 and you need to upgrade Xcode version in the future.