first, APP is defensively registered in categories 9, 35, 38 and 42 (related to software products and services)

but the above categories are not the core, because app is only a carrier, not a commodity or service that is really sold to consumers.

Second, the registered trademark of app should choose the category of core goods and services

This depends on what services your APP provides. Examples are as follows:

Alipay APP, which provides financial services, registered 36 categories;

Taobao APP, which provides e-commerce platform and sales, registered 35 categories;