Can i use Openstreetmap in react native for free with polygons and markers

Question

I'm about to integrate a map in my app and i have Openstreetmap as a candidate in the table, but i have some questions

1. Should i have a Google api Key to use Openstreetmap and, this means that Openstreetmap is not free ?
2. I've found some librairies that propose Openstreetmap in react native The fourth library don't ask for Google key like these : https://github.com/enieber/react-native-open-street-map

https://www.npmjs.com/package/react-native-open-maps

https://github.com/fqborges/react-native-maps-osmdroid

https://github.com/Splicer97/react-native-osmdroid

3. Can i use functionalities like : polygone, markers and so on with these librairies ? For the first two i didn't find any mentions about those components, in the third and fourth one they exist.
4. If i use polygons and markers with the third and fourth libraries, should i pay or i have to only get an api Key ?