I am creating a bunch of hosted feature layers from publically available data that will be useful to the community. Will those disappear when my subscription ends?
You will not be able to use any licenses. You will not be able to create new hosted content. Existing feature services, maps and apps won't be deleted (... maybe eventually?) but you will not be able to access them either.
My subscription has expired. My content is publicly shared but is no longer accessible to the public or users with paid accounts. I will need to renew my subscription for it to become available.
All settings, data, and items will be retained if your subscription expires but anything you have stored on the subscription will still incur credit charges and is likely to go into deficit. You will also be limited from accessing the content and you will not be able to create new content