According to https://xcodereleases.com Xcode 4.6 was released six years ago in January 2013. I think it is asking quite a lot to still be able to run this, even with a 2-year-old macOS installation. Xcode 8 is “only” 2 years old, but even that is pretty dated. Even if you could get Xcode 6 to run you wouldn’t be able to run code on real devices unless you’ve managed to keep one running a really old iOS version. I think Xcode 8 will only support as high as iOS 10.

I’m not sure what the current minimum Xcode version for uploading to the App Store is but, at the the time of writing, https://developer.apple.com/ios/submit/ says “Starting March 2019, all iOS apps submitted to the App Store will need to be built with the iOS 12.1 SDK or later, and support the all-screen design of iPhone XS Max or the 12.9-inch iPad Pro (3rd generation).”

That means Xcode 10.1 or later will be required to upload apps after March. Living on the bleeding edge is hard; trying to live 2–6 years in the past is probably harder still. Good luck!