depends on the app

you have something to access some cloud-api-stuff? yeah, probably all calls fail

some game that uses hardware-specific things? might break too

your average clock app or document viewer? that got a decent chance it'll still run.

It's a question of how fast your OS changes and how mature APIs have gotten. Android is a lot more stable now, than it was 12 years ago.

And if you look at truly mature OSes, like Linux or Windows, you probably can still run most apps that are multiple decades old. (For Win that means pretty much anything that was written for Win32(s) and newer - so even stuff that was around on Win 3.11)

That's when it's between the line of "You have to buy the hardware" and "Emulate it". Something too old for modern devices, and too new for emulators to have been made.

I still want to fucking play the original Infinity Blade. I WAS SO JEALOUS of my brother because he had his fancy Iphone 4 and could play. But by the time I got a phone it was already old news and taken off the app store.

I can still play 15+ old games on my Linux laptop with wine. It just works.