Not really, at least not in a sense that different products and stores compete. When I buy a phone I can choose from multiple models, then once I choose a mode

Not really, at least not in a sense that different products and stores compete. When I buy a phone I can choose from multiple models, then once I choose a model I can choose a store where I want to buy it. These 2 examples are competitive. Then I can choose what app I want to buy, but I can't choose anymore where I buy it (at least on IOS). There's no competition between stores. There's just competition between phone manufacturers that ends the moment you choose the phone, from then onwards is a monopoly (or near monopoly in case of Android)