WordPress woocommerce custom plugin compatibility

Hi ,
I want to purchase your plugin .But before that I need to be sure about some issues .

1. Will my custom plugin for woocommerce payment getway(or any other wordpress plugin) will work in my app ?
2.Will the app be workable after every new Android or iOS realese? Or I have to create new app to make it compatible with every new mobike os?
3. I have 2 sites perked in same server . Is there any discounts available for buying for 2 sites or I just have buy 1 time license for all my sites ?
4. Will my original wordpress theme be workable on my app.

Thank you.
Sabbir