Topstore is described as 'app allows you to browse through apps of various categories and let you download everything for free. It cannot be download from Apple Store can be downloaded from the link above'. There are nine alternatives to Topstore for a variety of platforms, including iPhone, iPad, Online / Web-based, Android and Windows. The best alternative is AltStore. It's not free, so if you're looking for a free alternative, you could try AppCake or TutuApp. Other great apps like Topstore are AppValley (Free), BuildStore (Paid), iOS Haven (Free, Open Source) and iPAST0RE (Paid).
AppValley allows you to browse through apps of various categories. The apps which you can’t download from Apple Store can be downloaded from AppValley. In fact, AppValley even allows you to have the modified (or tweaked/hacked) version of the app that you want to download.