Best Alternative App Stores for Android, iOS and Chinese Phones

After the operating system is App Stores are the most important software/app for any device. This is the place where you can install the apps to make your device more productive and more useful. Now every operating system has its own official App Store. For example, iOS has App Store, Android has Google Play Store/Huawei App Gallery. Chinese phones have their own store and computer operating systems have their own App Market.