[General Questions and Answers] Agret:
I agree it's good to backup versions of games and apps you like as in the future versions they can put in more paid stuff or extra ads that ruin the experience or even remove the app entirely from store.

One important thing to note about the ES Explorer / SAI exports is that they only backup the APK files not any of the userdata so if the game is a larger one that has to download extra data when you first install it then that extra data might become unavailable in the future, there is probably a way to back it up on the device too but you would have to do some searching.

--

XAPK file is the same as split apk, different apps have different methods of storing the split but they are both just a renamed zip file, they have a different manifest store within them to give app info though. I haven't tried renaming them to see if they work or not. You could create your own manifest file pretty easy by copying an existing one and just changing the package name to match your app that you downloaded.

When I open the apks file there is two files meta.sai_v1.json & meta.sai_v2.json which contain info about the app

{"backup_components":[{"size":101248459,"type":"apk_files"}],"export_timestamp":1602564855913,"split_apk":true,"label":"Camera","meta_version":2,"min_sdk":30,"package":"com.google.android.GoogleCamera","target_sdk":30,"version_code":63653876,"version_name":"8.0.018.335051840"}

xapk is what apkpure website uses, when I open it and one of the apks both in 7-zip the apkpure one has a file named manifest.json which contains info about the app package etc.

{"xapk_version":2,"package_name":"com.spryfox.tripletown","name":"TripleTown","locales_name":{"af":"TripleTown","am":"TripleTown","ar":"TripleTown","as":"TripleTown","az":"TripleTown","be":"TripleTown","bg":"TripleTown","bn":"TripleTown","bs":"TripleTown","ca":"TripleTown","cs":"TripleTown","da":"TripleTown","de":"TripleTown","el":"TripleTown","en-AU":"TripleTown","en-CA":"TripleTown","en-GB":"TripleTown","en-IN":"TripleTown","en-XC":"TripleTown","es":"TripleTown","es-US":"TripleTown","et":"TripleTown","eu":"TripleTown","fa":"TripleTown","fi":"TripleTown","fr":"TripleTown","fr-CA":"TripleTown","gl":"TripleTown","gu":"TripleTown","hi":"TripleTown","hr":"TripleTown","hu":"TripleTown","hy":"TripleTown","in":"TripleTown","is":"TripleTown","it":"TripleTown","iw":"TripleTown","ja":"TripleTown","ka":"TripleTown","kk":"TripleTown","km":"TripleTown","kn":"TripleTown","ko":"TripleTown","ky":"TripleTown","lo":"TripleTown","lt":"TripleTown","lv":"TripleTown","mk":"TripleTown","ml":"TripleTown","mn":"TripleTown","mr":"TripleTown","ms":"TripleTown","my":"TripleTown","nb":"TripleTown","ne":"TripleTown","nl":"TripleTown","or":"TripleTown","pa":"TripleTown","pl":"TripleTown","pt":"TripleTown","pt-BR":"TripleTown","pt-PT":"TripleTown","ro":"TripleTown","ru":"TripleTown","si":"TripleTown","sk":"TripleTown","sl":"TripleTown","sq":"TripleTown","sr":"TripleTown","sr-Latn":"TripleTown","sv":"TripleTown","sw":"TripleTown","ta":"TripleTown","te":"TripleTown","th":"TripleTown","tl":"TripleTown","tr":"TripleTown","uk":"TripleTown","ur":"TripleTown","uz":"TripleTown","vi":"TripleTown","zh-CN":"TripleTown","zh-HK":"TripleTown","zh-TW":"TripleTown","zu":"TripleTown"},"version_code":"5033","version_name":"2.0.1","min_sdk_version":"23","target_sdk_version":"28","permissions":["android.permission.INTERNET","android.permission.CHANGE_WIFI_MULTICAST_STATE","android.permission.ACCESS_NETWORK_STATE","android.permission.WRITE_EXTERNAL_STORAGE","com.android.vending.BILLING","android.permission.READ_EXTERNAL_STORAGE"],"split_configs":["config.arm64_v8a"],"total_size":31540018,"icon":"icon.png","split_apks":[{"file":"com.spryfox.tripletown.apk","id":"base"},{"file":"config.arm64_v8a.apk","id":"config.arm64_v8a"}]}