But now I was thinking of advertising as freelance app developer. I think the app works well but not sure if I can rightly call myself a mobile developer because it’s not using swift or android studio? I was wondering people’s thoughts and whether you think it’s fine if the app works?
Speaking as an experienced iOS/Android developer, it's not really about whether you use Swift/Xcode or Android Studio for development, but your knowledge and experience with the platforms, their SDKs, policies (for better or worse), and all the various "quirks" (for the lack of a better term) that make up mobile apps that really matter.
I haven't used Unity in quite a few years, so I'm not sure what control and visibility you have into the innards of iOS & Android when writing apps for those platforms, or how, for instance, Unity handles updates to the platform SDKs when they come out.
Like Casey said very early in the series, there's nothing inherently wrong with using Unity for game development, but understanding game engines makes you a more powerful Unity developer. I think the same applies here -- even if you commit to using Unity for mobile app development, gaining an understanding of the iOS & Android platforms and how to develop with their SDKs would be valuable.