Use APKPure App
Get Backup apk to SD old version APK for Android
SD 카드 또는 내부 SD에 백업 APK**** Plz은 저장 권한을 허용 ****
4 key feature
-app backup to sd
-install from sd
-uninstall from device
-share you app through facebook or whatsapp
**Don't forget to allow storage permission before user