_Auster_: On iOS
Not entirely sure, but some apps I used from the Play Store were no longer downloadable after they were removed (not sure if they were banned or simply delisted by the publisher's request). Worst case scenario, if possible, create an offiline back up of the game (although Google's DRM might be an issue in this case).
, re-installing delisted games used to be possible, but the last time I used an Apple device was ten years ago, so it might have changed. As I recall, you had to do it through iTunes, which I believe doesn't even support managing your apps anymore. For Android
, it's not possible, not even for apps you paid for
, which I know because that happened to be with an alarm clock app I once bought on Google Play. The developer when out of business, the app was delisted, and I never could get the app back after having uninstalled it. It still shows in my purchase and install history, but there is no way to install it.
The good thing about Android is that it officially supports side-loading, and there are some trustworthy APK archives out there that keep old versions of APKs that used to be available from Google Play. In a lot of cases, you can find the file there and re-install the app. Unfortunately, they of course don't archive paid apps. And the archives might be much more empty for recent stuff due to the switch from APKs to AABs on the Play Store.
The best way is to back up the apps you still have installed. This is pretty easy through enabling USB debugging and using adb (get list of installed packages, get path of specific package, copy .apk to computer). This way you can re-install it from your local copy later, unless the app has some other form of online DRM in it (I don't think Google adds anything, I never had any issue restoring apps from local backups).