Maybe just the circles I run in but these are not evergreen questions in my experience. I don't even know what "go back" is supposed to mean here, or for that matter what it would mean in a Windows application. Is there a system level "go back" in WinAmp/Excel/SimCity/Photoshop I've never seen before?
I was referring to IOS, not MACOS
Androids do have universal back button at the bottom on the phone or the same swipe gesture if you want but iphones do not.
Sometimes swipe (the direction and position is a guessing game), sometimes and x (right or left ) and the behavior is inconsistent too (back or close)
There are some guidelines but more often than not seems like every app has it's own method and you need to get used to it
In iOS, task manager and closure can't be overridden. You swipe right to return to previous application. You can swipe left for a couple of seconds if you didn't intend to do that.
You swipe up and remove the application from the stack, all processes of the application is killed.
Background processing has strict limits, and you need permissions to run longer than that, and for some use cases, there are no recourse. OS swaps you out or freezes the app.
If you want an app to work in the background, don't kill it, period. Push notifications are handled by the OS and is not hindered by this.
What about going "back" INSIDE an application?
Think for example reddit, you open a thread, how do you go back?
You open the "reply window, now ho you ho back? Maybe close it directly?
I Android this is all handled by the same function and is often ranked as the most frustrating design choice in IOS
I'm not using Reddit in any capacity since they have started giving their content for LLM training, so I can't help you with that, but looking at 4-5 third party applications right now, they all have a left arrow at top left to go back.
They all are very different applications and have very different designs, yet the arrow is there.
To be honest, I baffled at your question for a second or so, because I never thought about that, yet the method is so universal that I was not thinking about it at all.
There is a common way to go back (swipe from the left edge of the screen). Some apps just don't integrate well and ignore the platform patterns.
I believe swiping from left to right is common for both Android and iOS.
Android has both a swipe gesture or a widget that simulates buttons that used to be at the bottom of the screen
...and iOS has both an arrow at the top left and a swipe gesture. I can't see how they are that different.