Newbie on 3rd party access to database

I would really appreciate if you could help me with these newbie questions.Hope this is the right place to ask.

I`m analyzing the online app. development platforms at the moment. My target is to build and app for ios and android using the same code base. My app will consists of a user interface which allows user to input some personal data and and option to choose from.Based on the option app. will charge user an amount.

My questions is
1 - Is it possible to R/W access to database where user data is stored from a .net application on windows desktop ? Does share db connection information ?
2- (if respond to 1st questions is : No)Can I use 3rd party online database for my app build in to work with ?
3- Are there any regional constraints related to development or publish of the apps ? My target region for both platforms is Turkey

Kind Regards
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