iOS is based on Darwin which is BSD based, and Android is based on Linux, which is heavily inspired by Unix.
So technically, we are "all running some unix os on our phones"... perhaps you mean some open-source OS? Even then, Android markets itself as being open-source (although I imagine they must add some closed source stuff on top of it).
Apple XCode is required to compile code for Apple iOS. Android Studio is not required to compile code for Android.
Android Studio doesn't run on Android. XCode IDE doesn't run on iOS.
XCode IDE requires an MacOS device. Android Studio works on Win/Mac/Linux/Chromebook_with_containers.
Android Studio runs in a Linux container. XCode only runs on MacOS.
Apple does not allow, and per a recent ruling, and DOES NOT HAVE TO allow 3rd party app stores.
(There are already 3rd party app "stores" for Android like FDroid.)
Android already allows, and per a recent ruling, MUST allow 3rd party app stores.
In terms of Application stores, (after trying to trademark the phrase "app store" to anticompete Amazon) Apple gets protectionism for their walled garden, and Android may not have a walled garden.
iOS is based on Darwin which is BSD based, and Android is based on Linux, which is heavily inspired by Unix.
So technically, we are "all running some unix os on our phones"... perhaps you mean some open-source OS? Even then, Android markets itself as being open-source (although I imagine they must add some closed source stuff on top of it).