1. Yes
2.it is HSQLDB which is a flatfile database
3. device local storage refer : https://academy.mendix.com/link/paths/150/Model-and-Synchronize-Data-in-an-Offline-App
4. BLE: using connectors : https://marketplace.mendix.com/link/component/110411
NFC: using javascript actions https://docs.mendix.com/howto/extensibility/create-native-javascript-action/
5.you can built custom widgets : https://docs.mendix.com/howto8/extensibility/widget-development/
6.don't understand what you mean here.
7.Mendix allows the apps that you build to be deployed in any Cloud. This can be in the Mendix Public Cloud, Mendix Dedicated Cloud, Mendix Private Cloud, SAP Business Technology Platform, or in other on-premises and Cloud architectures. look here for more from 9: https://docs.mendix.com/support/#support-by-strategy
8. Mendix helps in build the packages but you need to publish them in respective store looks here: https://docs.mendix.com/howto8/mobile/deploying-native-app/
Regarding 1), HyperSQL (hsqldb) is the default database only for local development. In the Mendix cloud default is PostgreSQL (AWS RDS).
Regarding 2), local file storage is just the filesystem on your pc during development, in the Mendix cloud files are stored on S3.