How do you check/change iOS version in React Native?

I heard that a new version of iOS came out the other day, and wanted to know if my React Native project would be using that version by default when I build it with XCode, and if not, how can I force it to?

My Questions Are:

1) How do you check what version of iOS a React Native app is using?

2) How do you update the version of iOS in a React Native app?