Ask HN: Mobile Application Survey

My background: Proficient with angular/backend/frontend/database web/REST API development using Java ecosystem but in past have dabbled with Swift and built beginner iOS app as well (using Udacity course)

My goal: Build a (yet another) language learning application for languages spoken in India. Application will be heavy with audio/photos and possibly video.

Budget: I will build this in my spare time (I have a programming day job)

My questions: - Should I build it in iOS or Android? - Should it be native app or using react native or something similar - Should all media all be bundled with app so that no internet connectivity is required while using app? - Or should audio/video be streamed from backend - which will require connectivity to internet? - should it be a free or paid app? - is there already available text-to-speech apis/library for Indian languages or how I can build one? Any pointers highly appreciated!

Thanks