Advise for own app run in startup

Hey

I am thinking to build some App for tablets and for it I would like to run my own app once tablet is turned on ( to have only this app run)

Being honest I am a bit confused which options I can use here and which one is better..

The requirements from me is to have option to connect to api or have offline app in case of missing network connection, have memory management etc

Would like to also have option to support diff brands tablets like Sam,Apple, Huawei

As I See so far:

1.Own OS?
2. OS based on Android but then need to have jumps to higher version of Android or it is back compatible? What about ios?
3. Kiosk Mode for ios/Android?

Now the question is what else I can take into account to think about ?

Once app is already run on tablet I want only download the update but.. nothing else.. just to have the app running 10 years..;)

Any suggestions?

App to be created in python or java..

Please put the offer only if you know topic